Apple is hiring people with expertise in building medical sensors for activity, blood through the skin and more according to a report from 9to5Mac. The report says that Apple has hired Ravi Narasimhan from Vital Connect which develops wearable bio-sensors such as the "HealthPatch" which can be worn on the chest to monitor the users health and send data via Bluetooth, and Nancy Dougherty from Sano Intelligence who was in charge of hardware development at the company. Sano Intelligence have currently been working on what they call an "API for the bloodstream" but have yet to launch it. These aren't the only people with such experience at Apple. Last year, 9to5Mac reported that Apple was looking at several people from bio-medical start-ups and even people with fitness tracking experience.
Whatever Apple is doing it seem that it's likely to be much more of a leap forward than anyone else in the wearable technology sector is doing, however when we'll actually see it is still completely unknown.