The Apple Watch, announced on-stage at an event in California yesterday, didn't live up to the rumors that it would offer advanced health sensing -- rumors that built up around the "iWatch" thanks to months of reports about Apple's growing team of medical sensor experts.

Why did Apple hire a sleep expert like Roy J.E.M. Raymann from Philips Research -- a senior scientist at Philips Research who founded the Philips Sleep Experience Laboratory and who led projects related to sleep and activity monitoring -- if its wearable doesn't track sleep? While app developers or even Apple itself could take advantage of the sensors already built-in to the Apple Watch to add sleep tracking features, that probably won't make it a popular sleep tracker. At least not if you want it to wear it during the day too, because it needs to be charged at night.

“There’s a lot of new technology packed into Apple Watch and we think people will love using it throughout the day,” An Apple spokesperson explained to Re/Code on the sidelines of the Apple event yesterday. “We anticipate that people will charge nightly, which is why we designed an innovative charging solution that combines our MagSafe technology and inductive charging.”

Sleep tracking looks to be a long shot for Apple Watch owners any time soon, but Raymann isn't the only recent Apple hire that may seem puzzling now. 

Take Apple's hiring of medical sensor expert Marcelo Lamego, the former CTO of Cercacor, a non-invasive health-monitoring technology company focused on developer a device that could detect a patient’s pulse rate, hemoglobin levels, pulse ox, and perfusion index. Or the hiring of Ueyn Block, formerly of C8 MediSensors and Todd Whitehurst, a former Vice President at Senseonics -- both previously focused on attempting noninvasive glucose monitoring through the skin.

There were many other recent hires whose experience at seemingly much more ambitious medical sensor efforts have culminated in a wearable device from Apple capable of estimating calories burned, time active, pulse rate and little else in the way of health or fitness.

Or is it?

One sensor expert told MobiHealthNews that the Apple Watch appears to have a sensor array that is capable of much more than sensing pulse rate and activity. While Apple has yet to reveal technical specs of its Watch, images of the device show sensors on its underbelly that would appear to be overkill for a singularly-focused heart rate sensor.

As the sleep tracking debacle discussed above indicates, Apple's Watch has a battery problem. Wearable device makers like Misfit looked to solve the charging issue by loading their device with a coin cell battery that reportedly lasts for months. Jawbone's UP24 now boasts 14 days of battery life between charges. Of course, both of these devices largely rely on the wearer's smartphone screen since neither really has one.

Apple hasn't yet announced an official average battery life for its new Watch, an indication that they are still working to improve it in time for the promised "early 2015" commercial launch date. As a result, even if the device's hardware might be capable of supporting a variety of more advanced health sensing, there's little chance Apple is going to add it before it figures out how to improve battery life.

For the initial launch, anyway, it seems Apple chose a slimmer battery, a shorter battery life, and less advanced health tracking capabilities over a bulkier and, therefore, probably less fashionable-looking, advanced sensing device.

Another possibility is that before long, the three aesthetically different versions of the Apple Watch will have unique sensing capabilities. Maybe the Apple Watch Sport edition will offer more advanced all-day tracking capabilities along with a slightly thicker build to accommodate the needed power.

In any event, until the battery issues can be resolved, Tim Cook's description of the Apple Watch as "a comprehensive health and fitness device" remains dubious at best.