This short overview by Conor Hale succinctly captures the potential power and current limitations of using wearable devices such as the iWatch to alert users to changes in their vital signs, helping people and clinicians detect conditions such as atrial fibrillation.  

It is clear that we are going to see many more studies like this, from atrial fibrillation to diabetes, to epilepsy and really demonstrates some of the underlying changes happening in the industry, worth a quick read