This week MobiHealthNews once again rounded up an up-to-date list of health and wellness apps that connect to Apple's HealthKit, a health and fitness data exchange that makes it easier for iOS apps to share data with each other. For this week's in-depth report, MobiHealthNews analyzed the ways in which these 137 health and wellness apps are integrating with HealthKit. Some only pull data from HealthKit, while others only push data into HealthKit for other apps to use. A good number -- about 20 percent -- do both.

This is almost certainly not an exhaustive list -- apps continue to add HealthKit integrations everyday and Apple is slowly adding new fields to its platform. We also found two or three apps that claimed to connect to HealthKit but didn't make clear exactly what kinds of data they were sharing or pulling. We left these puzzling apps out of our analysis.

While HealthKit makes it possible to share dozens of different types of health and fitness data, most HealthKit-enabled apps are making use of the same few data points. Active calories and weight data are both among the top three most popular data types to push or pull from HealthKit. Heart rate data and step count is right up there, too.

Based on MobiHealthNews' analysis, here's a quick breakdown of the top 10 most popular data types pushed to HealthKit and the top 10 most pulled: 

Number of apps pushing various kinds of data (or "writing") to Apple HealthKit.

• 34 percent of HealthKit apps (46) are pushing active calories data.
• 20 percent of HealthKit apps (28) are pushing weight data.
• 18 percent of HealthKit apps (25) are writing heart rate data.
• 18 percent (24) are pushing workouts data to HealthKit, even though the Apple Health app doesn't have such a field.
• 15 percent of HealthKit apps (21) are feeding step count data into the platform.
• 15 percent (20) are sharing walking and running distance data with HealthKit.
• 10 percent of HealthKit apps (14) are pushing out sleep analysis data.
• 9 percent (12) are sharing nutrition data with the HealthKit ecosystem.
• 8 percent (11) are pushing out blood pressure data with HealthKit.
• 7 percent of HealthKit apps (9) are writing cycling distance data.

Number of apps pulling various kinds of data (or "reading") from Apple HealthKit.

• 23 percent of HealthKit apps (32) are pulling weight data.
• 16 percent (22) are integrating step count data from HealthKit.
• 12 percent (17) are using active calories data from the platform.
• 10 percent of HealthKit apps (14) are using heart rate data pulled from the system.
• 10 percent (14) are pulling down blood pressure data from HealthKit.
• 9 percent (13) make use of walking and running distance data retrieved from HealthKit.
• 9 percent (13) are pulling nutrition data from HealthKit.
• 9 percent of HealthKit apps (12) are using sleep analysis data from the platform.
• 7 percent of HealthKit-connected apps are using the platform to pull in a user's height.
• 7 percent (9) are pulling in a user's birthdate from HealthKit.

We'll share topline metrics on pricing data for these 137 apps later in this in-depth. 

Discussion: The provider and payor apps integrated with Apple's HealthKit

The vast majority of the apps integrating with HealthKit are fitness-oriented trackers. But one of the things that Apple leaned on the most when they announced HealthKit was that the platform could also be used to improve healthcare, which they illustrated via their partnerships with Epic and the Mayo Clinic. Our analysis found 15 apps that interfaced with providers and another three related to payers and employers.

Patient engagement apps working with HealthKit

Telemedicine and patient engagement apps made up seven apps on this list. American Well, which has two HealthKit-enabled apps, currently has the only HealthKit integrated video visits app that we could find. The app pulls heart rate, blood pressure, body temperature, weight, nutrition, respiratory rate, and blood glucose in from HealthKit so users can choose to share it with their doctor during a video call. American Well bullishly announced their HealthKit integration in a press release at the end of September:

“By bringing HealthKit insight to a live doctor visit, Amwell introduces a revolution in follow up and treatment of chronic patients,” Dr. Roy Schoenberg, CEO of American Well, said in a statement. “Apple’s elegant entry into home and biometric healthcare, coupled with the power of telehealth, is poised to create a new ecosystem where fact-based, quality healthcare can be delivered by live physicians to those who need it most — chronic, home-bound patients. This is no less than the beginning of a new era in home care delivery.”

Another app, the eponymous First Opinion, takes a lower-tech approach to telemedicine, connecting patients to a doctor via text. HealthKit enables the patient to share a little more health information with their doctor.

A few additional apps in this subcategory support doctor-patient communication in other ways. Dr. Jordan Shlain described HealthLoop's HealthKit integration at a recent Boston event, for instance, saying that they would start out using HealthKit to help doctors keep an eye on movement data in post-surgical patients. Patient IO by Filament Labs is also meant as a way for providers to keep in touch with patients post-discharge and also uses HealthKit to help patients track health metrics to send to their doctors. YingoYango, which connects care teams to one another, uses HealthKit data to help keep everyone on the same page with a patient's progress.

Finally, two symptom checker apps made the list, from large companies that have been moving more into the realm of patient engagement. WebMD's app and ShareCare's AskMD app both offer tracking capabilities, and are starting to share that tracking data out with HealthKit. ShareCare also pulls some basic data in from HealthKit.

EHRs and PHRs

A few medical-related apps came from EHR vendors or served as stand alone personal health records. Of course, Epic's MyChart app, which was announced from Apple's WWDC stage at the initial launch of HealthKit, is one such app. But Cerner has a HealthKit-enabled app, HealthyNow, as well. It reads step data from HealthKit and uses it to encourage patients to move more. No sign of an actual Allscripts HealthKit integration yet, despite rumors of one earlier this year.

One smaller EHR player, drchrono, is in on the HealthKit game as well, though not for its main mobile EHR product -- possibly because HealthKit is not available for the iPad. Instead drchrono is using HealthKit for its onpatient PHR, which will read at least weight, blood pressure and heart rate from HealthKit. Another PHR app, Hello Doctor, is also integrated with HealthKit.

Payers and providers

Two insurance companies have apps integrated with HealthKit so far: Humana with its HumanaVitality app and the Health Care Services Corporation (HCSC) with its Centered app. Both are basically wellness tracker apps for members. A third app in that category is the app from Virgin Pulse, formerly Virgin Healthmiles, an employee wellness provider. Their app, of course, connects to the Max activity tracker as well as to HealthKit.

When it comes to direct-from-provider apps, only the Mayo Clinic itself -- another Apple poster child -- showed up in our searches. Axial Exchange, which makes apps for a number of hospitals and hospital systems made a blog post claiming to have HealthKit support for those apps, but we weren't able to verify that any of the hospitals had yet taken up Axial Exchange on the offer.

"The Axial patient app will pull data from the following HealthKit categories: height, step count (for our activity tracker), body mass (for our weight tracker), blood pressure (systolic/diastolic) and heart-rate (for our cardio tracker), blood glucose (for our glucose tracker) and sleep analysis (for our sleep tracker)," the company told MobiHealthNews in an email. "Axial is also adding sharing of the user’s weight, blood pressure and heart rate, and blood glucose." 

Topline pricing data for HealthKit-enabled apps

With such a small data set there's likely little to be gleaned from the pricing trends of today's HealthKit-enabled apps. In case it is of interest, about 76 percent of HealthKit apps (103) are free. About 9 percent of these apps cost $2.99, while 6 percent cost $0.99. About 3 percent cost $1.99 and an another 3 percent cost $3.99. Finally, 4 percent cost $4.99 or more. One of the apps requires a monthly subscription and at least nine of the apps offered up in-app purchases.

Who -- and what -- are still missing from Apple's HealthKit?

Even though there are already at least 137 apps that integrate with HealthKit, there are thousands of other health and fitness apps in the Apple AppStore that don't. Yet, it was a surprise to find that certain popular apps and some important tracking features were not yet a part of Apple's HealthKit ecosystem.

One large section that is missing from HealthKit is fertility tracking. While Clue and Ovia, two fertility apps, are included in MobiHealthNews' Appendix I below, the apps only send one metric to HealthKit that's related to fertility -- basal body temperature. And even then, Ovuline and Clue has to store this data in HealthKit's normal temperature section, so if these fertility trackers are using HealthKit to collect basal body temperature, they cannot integrate any regular temperature data along with it because it wouldn't be differentiated. Of course, it's also important to note that MobiHealthNews did not find any connected thermometers that sync with HealthKit. Other important fertility-related metrics missing include period cycle, cervical fluid, and birth control tracking.

Another absent section is pill tracking. Though HealthKit tracks inhaler usage and will eventually track blood glucose (again) -- two metrics used for chronic disease management -- there's no option for tracking whether you took a pill or not. Just last year, MobiHealthNews found that at least 8 pillboxes connect to smartphone apps. There are also no apps created by pharma companies currently integrated with HealthKit. This may be in part because, as Research2Guidance (R2G) found in a recent report, pharmaceutical companies have a lot of apps in the market, and have been making apps for a long time, but their apps aren’t seeing downloads and usage on par with the apps from other industries.

Some popular apps and devices have also chosen not to integrate with HealthKit. Last month, Fitbit posted in its online customer feedback forum that it had no current plans to integrate with the platform. At the time, MobiHealthNews speculated that Fitbit might be taking a stand against HealthKit because Fitbit doesn’t see itself benefitting from the integration in the long term. And then, Apple began pulling Fitbit devices from its physical and online stores. Another popular device that does not integrate with HealthKit is Intel's Basis, but that may be because Basis' new device, the Basis Peak is positioning itself as a competitor to the Apple Watch.

One popular fitness app that hasn't integrated with HealthKit yet is RunKeeper, however, the company has said that they plan to sync their app eventually. On the company's feature requests page, a RunKeeper spokeperson explained that while they plan to integrate RunKeeper into HealthKit, the RunKeeper team is "doing the necessary research and development" to make sure that HealthKit is stable and that RunKeeper customer data will be secure. It's also significant to note that, in 2011, RunKeeper created a similar platform to HealthKit, which they called Health Graph. At the time, the company explained that Health Graph would allow users to see a unified view of workout data, social interactions, diet, and sleep habits in the aim of tracking and improving the user's overall health and fitness. Finally, iHealth integrated three of its four apps into HealthKit. The medical device maker left out iHealth Gluco-Smart, which tracks blood glucose.

Two sections that are not in HealthKit right now, but likely will be added eventually are workouts and blood glucose. In June, when Apple first announced HealthKit, Rock Health published a blog post reaction to HealthKit that pointed out one of the slides Apple presented during the event had the wrong measurement units for blood glucose monitoring. And then last month, the company pulled the glucose tracking feature out of its Health app for users in some countries where glucose is tracked in millimoles per liter (mmol/L) and not milligrams per deciliter (mg/dL) like they are in the US. (This might be why iHealth hasn't integrated its glucose device yet.) While the platform does not currently have a glucose measuring option, several other app makers have explained that they plan to add glucose measurement when Apple brings the field back. Another section that has not yet been added is "workouts".  Some fitness apps claim to send workout data to HealthKit, but that's a field that has not shown up yet in Apple's Health app. Runtastic explained in a blog post that they are sending the data to HealthKit and it is being stored there until Apple makes it visible to users in the Health app. 

Appendix I: HealthKit-enabled apps that require (or strongly suggest) a peripheral health or fitness device

As part of our analysis we also looked for HealthKit-enabled apps from hardware makers. The iPhone's sensors are capable of generating some health-related data but for data fields like blood pressure, blood glucose and others, the smartphone alone isn't enough. Which devices are feeding third party sensor data into the HealthKit ecosystem? Here's a rundown, including what the devices' apps claim or appear to be sharing.

Beddit App name: Beddit Price: Free Description: This app connects to Beddit’s in-bed sensor that tracks a person’s total sleep time, sleep cycles, average heart rate, average respiration rate, heart rate curve, and night time events like bed exits and snoring. Beddit's sensor costs $150. Read: None Write: Sleep Analysis, Heart Rate

Bowflex App name: Bowflex MAX Trainer Workout Price: Free Description: The Bowflex Max Trainer effortlessly syncs with your Bowflex Max Trainer to track total calories burned, time, and watts. Bowflex trainers start at $999. Read: None Write: Active calories, Heart Rate, Workouts

Breathometer App name: Breathometer Price: Free Description: The Breathometer App supports all Breathometer products including: the Original Breathometer and Breathometer Breeze. Breeze costs $99.99 and the original costs $49.99. Read: None Write: Blood alcohol content

Garmin App name: Garmin Connect Price: Free Description: TOwners of Garmin activity tracking devices can use Garmin Connect to sync all of their workout data. Garmin trackers range from $129.99 to more than $400. Read: None Write: Steps, Active Calories, Walking + Running Distance

iHealth App name: iHealth MyVitals Price: Free Description: iHealth’s integrated mobile app works seamlessly with iHealth’s current line of self-monitoring mobile health devices, such as the body analysis scale and blood pressure monitors, and will integrate with future related products. Prices of these devices start at $69.95. Read: None Write: Blood Pressure, Heart Rate, Steps, Distance, Active Calories, Sleep Analysis, Weight, Body Mass Index, Body Fat, Lean Body Mass

iHealth App name: iHealth MyVitals 2.0 Price: Free Description: The app provides instant access to your measurements from iHealth devices and allows you to see how you are doing versus goals and tells you how you are doing versus published medical guidelines for key measurements like blood pressure. The app supports the iHealth Blood Pressure monitors, the iHealth Scales, the iHealth Pulse Oximeters and the iHealth Activity and Sleep Trackers. Prices of these devices start at $69.95. Read: None Write: Blood Pressure, Heart Rate, Steps, Distance, Active Calories, Sleep Analysis, Weight, Body Mass Index, Body Fat, Lean Body Mass

iHealth App name: iHealth SpO2 Price: Free Description: The iHealth SpO2 mobile app works seamlessly with the newest product to the iHealth suite, the Wireless Pulse Oximeter. The iHealth SpO2 measures and tracks your blood oxygen saturation (SpO2), pulse rate (BPM), and perfusion index. The pulse oximeter costs $69.95. Read: None Write: Oxygen Saturation

Jawbone App name: UP - Tracker Required Price: Free Description: Jawbone's UP devices track activity, diet and sleep to help users improve their health. UP Move costs $49.99, UP24 costs $129.99, and UP3 costs $179.99. Read: Steps, Sleep Analysis Write: Steps, Sleep Analysis

KHN Solutions App name: BACtrack Price: Free Description: Easily estimate your BAC (Blood Alcohol Content) with a BACtrack smartphone breathalyzer and the free companion app. The cheapest version of this tool is $49.99. Read: None Write: Blood alcohol content

Misfit Wearables App name: Misfit Price: Free Description: Shine is the activity and sleep tracker that prompts users to live an active life. Shine costs $99.99. Read: None Write: Steps

Netwalk App name: Heartbeats Price: $2.99 Description: This app is designed to work with the Pebble smartwatch and it is built to integrate with any Bluetooth heart monitor and report the user's current heart rate, workout time, calories burnt, running distance, and speed. The Pebble watch costs $99. Read: None Write: Heart Rate, Running + Walking Distance

Philosys App name: Gmate Smart Price: Free Description: This app, Gmate Smart is designed to help diabetics measure their blood glucose. You would need an additional device that is connected to iPhone, iPad or iPod to test your blood glucose as Gmate SMART will show you. Read: None Write: Blood Glucose

Qardio App name: Qardio Price: Free Description: This app connects to Qardio’s recently FDA-cleared connected blood pressure monitor, called QardioArm, which costs $99. Read: None Write: Blood Pressure, Heart Rate

ResMed App name: S+ Price: Free Description: Use this app with the S+ unit to monitor your sleep accurately and get personalized feedback and suggestions that can help you get to sleep faster and improve the quality of your sleep. The S+ costs $149.99. Read: None Write: Sleep Analysis

Wahoo Fitness App name: Wahoo Fitness Price: Free Description: Wahoo Fitness is a running, cycling and fitness app that leverages the iPhone to track cycling and running. It aims to help users reach their training and fitness goals. Devices start at $49.99. Read: None Write: Heart Rate, Active Calories, Distance Analysis

Withings App name: Health Mate Price: Free Description: Withings’ app, Health Mate, syncs with all Withings devices, including the Withings smart scales, activity trackers, sleep tracker, blood pressure monitor, and baby products. Withings products range from $99.95 to $390.00. Read: None Write: Heart Rate, Weight, Sleep Analysis, Steps

Appendix II: Quirky, unexpected HealthKit-enabled apps

There's a general pattern to most of the apps that take advantage of HealthKit, namely wellness self-tracking fare. But the list also has some quirky outliers that use HealthKit data in interesting and novel ways. Here's a few HealthKit-enabled apps we didn't see coming.

Deadline -- This $2.99 app pulls HealthKit data and compares it to demographic data to generate a countdown clock to the user's statistically likely moment of death. Change your workout or eating habits, your health data will change, and maybe Deadline will give you a few more years. The app has received plenty of attention, both from its fans and those who think the morbid approach to fitness is in poor taste. "I love this app," says one reviewer. "We all talk about being healthier, but seeing your time tick down by the second really makes you want to do something about it!"

Wokamon -- Remember virtual pets? Popular in the 90s, they were little virtual creatures that required simulated care, feeding, and often real-world walking as measured by a pedometer. Wokamon takes this idea into the smartphone age, with animated avatars that level up based on movement data brought in from HealthKit, Fitbit, Jawbone, or Moves.

Carrot Fit -- If the threat of your impending doom or the opportunity to care for an imaginary creature doesn't get you moving more, maybe submitting to verbal abuse from Carrot, a snarky fitness coach, will do the trick. With HealthKit, the app description says, Carrot will comment on workouts you logged with other apps entirely.

On Campus -- North Carolina State University has proactively taken on the "Freshman 15" with its student app, building in a food journal for students that syncs with HealthKit. It sits in the same Dining section of the app that lists the menus for the University's dining halls, so students can just tap a meal to add it to the log.

Panera Bread -- The casual restaurant chain is the only restaurant with HealthKit integration as far as we can tell. Like students at the NCSU dining hall, diners at Panera can select a menu item and import it directly into HealthKit's nutrition section. If other restaurants follow suit -- and popular food logging apps like Lose It! and MyFitnessPal sync with HealthKit's Nutrition database, food logging could get a whole lot simpler.

Just Dance Now -- Just Dance Now is a dancing game from well-known game developer UbiSoft. The game uses the iPhone as a controller and a laptop or iPad as a screen. As a bonus, the game tracks calories burned while playing and uploads them into HealthKit.