The big digital health story this week was, without a doubt, Apple's unveiling of ResearchKit, a forthcoming developer tool that will make it easier for medical researchers to use apps to collect health data for clinical studies. (If you haven't already, be sure to read our original coverage of the ResearchKit announcement right here.) What follows is a comprehensive round-up of the most important ResearchKit-related coverage from around the web, including some of the more interesting interviews, concerns, and benefits of Apple's new initiative.

At the end of this in-depth is a description of each of the first five ResearchKit-enabled apps that Apple announced on-stage on Monday. Those include: The University of Rochester and Sage Bionetworks' Parkinson’s research app, mPower; MGH's diabetes research app, GlucoSuccess; Stanford and the University of Oxford's heart disease research app called MyHeart Counts; Mount Sinai Hospital and Weill Cornell Medical College's asthma research app, Asthma Health; Dana Farber Cancer Institute, UCLA School of Public Health, Penn Medicine, and Sage Bionetworks' app for breast cancer survivors, Share the Journey.

Here's our ResearchKit media coverage round-up: 

Cook tells Mad Money's Jim Cramer mobile health market is "significantly underestimated": In a TV interview with Jim Cramer, Apple's CEO referred to mobile health as the biggest frontier of all:

Cramer: I know that the car, the home -- do you think of them as connectivity, social mobile cloud connectivity -- do you think of them as the next frontiers, or is there a frontier that I am missing, I'm not thinking big enough.

Cook: Well I think those two are big ones, that you talked about, I think health may be the biggest one of all, because for years people have depended on, strictly, somebody else to determine their health and now these devices in essence empower people to manage and track their own health and fitness. And so I think that market is probably significantly underestimated.

Cramer: Well let's go there because I know my cardiologist, working on the Stanford project, knows about it, and told me that it's within our lifetime that we will have your watch and your watch will show whether my blood pressure spike, which it did by the way when you called because I had no idea you were calling, but we will have, from your watch, diabetes, maybe blood pressure, maybe even cancer, because of the great app system that you have and because of the HealthKit -- do you think this is within the realm of our lifetime?

Cook: Oh, I absolutely do.

See the whole clip over at CNBC

It's open source so what about Android? Fortune's Dan Primack made it clear that while ResearchKit might be helping researchers connect with a larger pool of study participants, it could be much, much bigger.

"Only 14.8 percent of global smartphone users currently run iOS, which is the only operating system on which ResearchKit apps can be built. And that’s actually down a bit from 2013, according to IDC. A whopping 81.5 percent of global smartphone users run Android," he writes. "In other words, the vast majority of patients will be excluded from ResearchKit-based trials."

MobiHealthNews' own Jonah Comstock picked up on that thread and looked into why the open source ResearchKit may still have some trouble porting to other smartphone platforms, like Android. He writes:

The truth is, whether the platform will work with Android phones is still an open question. The API won’t be available for another month. So far, the five apps that have been released have been iOS apps, and the scope of their research is limited to Apple users. John Wilbanks, the Chief Commons Officer at Sage Bionetworks, which worked on two of the five initial apps, said that right now those apps work on Apple phones for logistical reasons.

“On a pragmatic level, there’s not very much variation among the sensors between those three [iOS] phones,” he said. “The gyroscopes, the accelerometers, the GPS; the chipsets are pretty much the same. That makes it pretty easy from a scientific perspective to normalize the data. When you get to the Android thing, a big part of the challenge is going to be normalizing across different hardware devices.”

PCWorld interviewed Alan Yeung, a cardiologist at Stanford Medicine who was involved with the development of that hospital’s ResearchKit-enabled app, MyHeart Counts. Leung told the publication he'd like to see ResearchKit for Android so the studies aren't only inclusive of iPhone users. He said: “Apple agreed with that as well.”

The lack of Android support means ResearchKit has a diversity problem: BuzzFeed points out that Apple iPhone users tend to be younger, better educated and wealthier than the many millions of people in the US who are not iPhone users. For example, black mobile phone users are more likely than white mobile phone users to have an Android device. The median iPhone user makes about $85,000 a year. By contrast, diabetes and cardiovascular diseases disproportionately affect African-Americans, and Parkinson’s disease is usually diagnosed in people around age 62. Asthma disproportionately affects kids, lower-income families and minorities. The list goes on and on. Read more over at BuzzFeed

Concerns about patients not being with researchers in-person: GlobalData’s medical devices analyst, Niharika Midha, said in a statement that ResearchKit "has the potential to redefine the medical research dynamics, especially for chronic disease management. The ability to recruit a large patient pool using iPhones will both reduce the costs associated with these studies and enable continual and convenient monitoring, as the patient does not have to visit a test center to record any data. The ability to link apps to other external wearable or monitoring devices, such as inhalers, is another distinct highlight of this technology."

Beyond privacy concerns, Midha said "it is uncertain whether this approach to medical research, in which physicians do not actually engage with participants, will add any valuable insight. This is because there are risks in assuming high participant compliance and formulating disease management conclusions based solely on the data collected by the ResearchKit." Therefore, ResearchKit can only be a supplement to the traditional methods.

The novelty factor will wear off for participants, then what? Midha is also concerned that ResearchKit apps will draw in a large group of users initially but will see significant drop-offs in participation during the course of the study. "This would make the previously-collected data unusable for the purposes of statistical analysis, although some form of incentive might sustain participant commitment. We therefore anticipate that the trade-offs between a large participant pool and data accuracy will be the top concerns of using this platform."

The apps don't know if you are who you say you are: "We are less worried about fraud and trolling and impersonation because there's a fair amount of work involved in being in this study, and doing it just for fraudulent purposes is kind of a strange behavior," Sage Bionetworks' Wilbanks told The Verge.  "People might do it for shits and giggles for a week or two, but I can't see someone doing voice testing and gait testing for 52 weeks when there's no sort of public pay off."

Kamal Jethwani of Boston-based Partners HealthCare told Politico: “I was able to sign up as a diabetes patient, someone who has Parkinson’s disease and someone who has asthma on the ResearchKit apps, yet I have none of those conditions. How will researchers separate noise from signal? And even if they can do that, the overhead involved in cleaning the data may just not worth it. I think more needs to be built into the process to keep only qualified patients in it.” He acknowledged that getting the word out to many more people than would typically hear about a clinical trial is an intriguing aspect of the launch though.

A larger skewed sample is still a skewed sample: “Just collecting lots of information about people -- who may or may not have a particular disease, and may or may not represent the typical patient -- could just add noise and distraction,” Lisa Schwartz, professor at the Dartmouth Institute for Health Policy and Clinical Practice, told Bloomberg. 

Halamka applauds Apple: In its initial coverage of the ResearchKit launch, Politico quoted Beth Israel Deaconess Medical Center CIO John Halamka celebrating the move: “Voluntary contribution of personal data in support of clinical research is real medical altruism. I applaud Apple for providing the middleware which makes this easy for researchers and secure for patients.”

Useful for a handful of diseases only? The publication also got a reaction from Christoph Lehmann, a professor of pediatrics and biomedical informatics at Vanderbilt University, who threw some cold water on the initiative's prospects: iPhone data will only be useful for a handful of disease states, he said.

HealthKit is buggy so ResearchKit will be, too: ReadWrite's Owen Thomas has been one of the toughest critics of Apple's spate of recent health product launches. His take on ResearchKit was no different:

"The problem with ResearchKit is that Apple's HealthKit software and its companion Health app are horribly buggy, hard to use, and unappealing to consumers. They don't even come close to our expectations for Apple products. They come from some alien planet closer to Microsoft," he writes. "Since ResearchKit is built on top of HealthKit, then that means it has shaky foundations indeed."

Thomas speculates that ResearchKit may signal an acknowledgement from Apple that HealthKit-enabled apps aren't taking off, and this recent launch helps explain away why Apple spent so much time and effort on health in recent months.

Apple updated the rules for iOS developers using ResearchKit: BuzzFeed noticed that Apple updated its guidelines for app developers to include new ones for using HealthKit and ResearchKit in human-subject medical studies. Here are three new excerpts from Apple's guidelines:

"Apps using the HealthKit framework or conducting human subject research for health purposes, such as through the use of ResearchKit, must comply with applicable law for each Territory in which the App is made available," Apple writes.

Apple is restricting data-mining and sharing data with third parties:

"Apps may not use or disclose to third parties user data gathered from the HealthKit API or from health-related human subject research for advertising or other use-based data mining purposes other than improving health, or for the purpose of health research."

The company also outlines best practices for obtaining consent:

"Apps conducting health-related human subject research must obtain consent from participants or, in the case of minors, their parent or guardian. Such consent must include the (a) nature, purpose, and duration of the research; (b) procedures, risks, and benefits to the participant; (c) information about confidentiality and handling of data (including any sharing with third parties); (d) a point of contact for participant questions; and (e) the withdrawal process."

Can researchers resell data to third parties? Those updates will likely put some concerns to rest about what happens to participants' data. Early media coverage of ResearchKit flagged the possibility of data misuse.

PopSci interviewed Michael Ostrolenk, the director of the Liberty Coalition, who is skeptical about the privacy protections in place for ResearchKit participants.

“The form usually says how [the organization] can release your data for treatment or healthcare operations—the scope is so wide that it destroys any thoughts we might have for privacy,” he said. “Especially now with so much information online, anything they say has medical privacy is mistaken to begin with.”

The first version may not get it right, but eventually, ResearchKit will prove to be a game-changer: In an enlightening interview with Quantified Self's Ernesto Ramirez, Sage's Wilbanks shared his vision.

"Once we start getting that engagement, and we begin to see a diverse ecology of applications built on top of ResearchKit, then we’ll start to see success. It may take a bit of time. It won’t happen with this iteration. Maybe not even the second, but when we get enough devices, apps, participants, and improved interoperability between them all we’ll start to see the power of network effects," he said.

"But, we’ve just started," Wilbanks said. "The fun now is that we get to test it. I’ve always said that we can’t screw it up any worse than it already is. This isn’t the end. It’s not finished. We’re going to keep changing and learning."

Read on for more on the first five ResearchKit-enabled apps that Apple announced earlier this week: 

Asthma Health by Mount Sinai -- Icahn School of Medicine at Mount Sinai, Weill Cornell Medical College, LifeMap Solutions

Asthma Health received 2,500 sign ups by Tuesday morning, one day after the app was announced. The app aims to help patients adhere to their treatment plans and avoid asthma triggers. Patients can use the app to record daytime and nighttime asthma symptoms as well as how they affect the patient’s activities. It also tracks daily usage of controller and rescue inhalers along with asthma triggers: colds, increased physical activity, strong smells, exhaust fumes, house dust, peak flow, and animals. Finally, it tracks emergency department visits, medical visits, and changes in medication. The app will also send updates about when users should take medication and what the air quality is like in a specific location.

To join the study, users need to be 18 or older, have asthma confirmed by a doctor and be prescribed medication for asthma. If the participant smokes, has another lung condition, or has congestive heart failure, they can’t participate.

Share the Journey -- Dana-Farber Cancer Institute, Penn Medicine, UCLA’s Jonsson Comprehensive Cancer Center, Sage Bionetworks

The app aims to analyze why some breast cancer survivors recover faster than others, why patients’ symptoms vary over time, and what can be done to improve their symptoms. The app will send patients questionnaires and collect sensor data to track five common symptoms of breast cancer treatment: fatigue, mood, cognitive changes, sleep disturbances, and changes in exercise. ResearchKit will pull data from HealthKit to collect data on steps, sleep, and the patients’ birthdate, height, and weight. Patients will also contribute to an in-app diary about their data. According to Sage Bionetworks, recording this data should not take longer than 20 minutes per week.

This study received funding from the Robert Wood Johnson Foundation. To participate in the study, the patient must be a woman between the ages of 18 and 80. 

Parkinson mPower study app -- University of Rochester, Beijing Institute of Geriatrics, The Michael J. Fox Foundation, Sage Bionetworks

This app received 5,589 sign ups by Tuesday morning, one day after the app was announced. mPower stands for “mobile Parkinson observatory for worldwide, evidence-based research”. The app description explains that although “living with Parkinson disease means coping with symptoms that change daily,” these changes are not tracked frequently enough. The mPower app aims to help users track their symptoms using activities including a memory game, finger tapping, speaking, and walking. The app will also collect data from wearable devices. Although the app aims to further research in Parkinson disease, the researchers encourage people with or without Parkinson disease to download the app.

GlucoSuccess -- Massachusetts General Hospital

This app was developed to help the hospital's research team create a crowd-sourced database of health behaviors and glucose values for people with type 2 diabetes, but the researchers also aim to help patients learn how their behaviors affect their health. Participants will track activity duration and intensity, diet information, blood glucose measurements, body weight, and waist size. The app will help remind users to log blood glucose data and record diet information through nutrition tracking app LoseIt. Using this data, GlucoSuccess will be able to provide users with insights into how their fitness and nutrition data relate to “finger-stick blood glucose values”. Participants must be 18 or older, live in the US, and have an existing diagnosis of pre-diabetes or diabetes. 

MyHeart Counts -- Stanford Medicine

MyHeart Counts received 11,000 sign ups by Tuesday morning, one day after the app was announced. The app aims to help the medical organization improve their understanding of heart health. MyHeart Counts measures activity through the Apple Watch, which offers a heart rate sensor, sensors in the iPhone, or a third-party wearable activity device linked to Health app. It will also ask users — who are able — to complete a six minute walk test. If users sync their cholesterol results and blood pressure, the MyHeart Counts app will also calculate their risk for future heart attack or stroke and provide them with a “heart age.” Participants must be 18 years or older, based in the US, and able to understand English.