The agency has published a draft guidance note that, as yet, isn't legally binding and requests opinions from the public. As far as it's concerned, "general wellness devices," i.e. watches that vaguely encourage people to get fitter, aren't any sort of risk to the public. This means that your Fitbit is okay to tell you to go for a walk, your Aura can coach your sleeping and Lumosity can pretend to make you smarter without any worries. Mostly the FDA is concerned with risk, and there isn't much risk if your smartphone tells you to lay off the burgers one every now and again.
If, however, the device begins to make specific claims about its uses, it's another story all together. If you see a product that promises to treat your obesity, autism, muscle dystrophy or erectile dysfunction -- plus anything that's physically invasive or prosthetic -- then the gear will have to jump through the FDA's numerous hoops.
Of course, as the world of fitness wearables matures and we see more medical applications for this tech, it's likely that the FDA will probably take another look at this area. After all, there were plenty of devices that we saw at CES that look a lot more like gear you'd find in a hospital than in a Best Buy.