Apple has even more secret health aspirations than anyone realized, according to reporting by Christina Farr for CNBC yesterday. Citing sources inside the company, Farr reports that Apple has a small offsite team dedicated to diabetes research that's been working for about five years.

The goal is one many other tech companies are working on but no one's close to cracking: noninvasive, continuous glucose monitoring. The company is apparently in the midst of feasibility trials and has started to investigate regulatory pathways. Emails between Apple and the FDA uncovered last year by MobiHealthNews contained no mention of the initiative, so if the company is in contact with the agency that communication began fairly recently.

Rumors that Apple is working on glucose tracking from the wrist aren't new. Apple hired several high-profile health folks back in 2013 including Ueyn Block, the former Director of Optics & Systems Engineering at C8 MediSensors, and Todd Whitehurst, the former Vice President of Product Development at Senseonics. Both Whitehurst and Block's previous experience was in glucose sensing. But when the Apple Watch debuted without a sophisticated sensor suite -- and reports of unexpected technical challenges -- many assumed the glucose sensing project was shelved.

If true, this is an ambitious project for Apple. There's currently no way to reliably, accurately measure blood glucose without actually drawing blood, either through tiny needles in a CGM or with a fingerprick device. Google's Verily, among others, is experimenting with getting glucose from tears via a contact lens, and some promising early research is focused on getting glucose readings from sweat. Apple's approach, according to reports, is to use an optical sensor to determine glucose value from blood without a needle.

In order for the device to be useful, it will have to not only monitor glucose levels, but do so accurately enough that people with diabetes can dose their insulin based on its measurements. That's a high bar that will involve a lot of development and rigorous proof to the FDA. As a point of comparison, CGMs have been around for a decade and the agency just recently allowed a CGM to be used for dosing insulin without additional readings from a fingerstick glucometer.

But if Apple can crack noninvasive glucose monitoring, the market opportunity is undeniable: the CDC reports that 9 million Americans are currently living with diabetes, and a way to track their glucose without breaking the skin would be a game changer.