forget quasi-medical apps, porn is the answer
The existing BP, pulse and temperature apps on wrist devices and mobile phones are of questionable accuracy. Skin-contact testing for factors currently determined by blood test are a long way off. Even were they available the market for any specific blood test analog would be limited to the tiny % of the population who need that specific parameter to be continually monitored.
The "killer apps" of many technologies have been and will remain porn and entertainment dating right back to cave art. The human psyche hasn't changed much in 30,000 years!
To capture the mass market a smart watch needs a camera capable of discretely capturing "candid" images (the reason many places banned Google Glass) and a not very intellectually challenging game (q.v. flappy bird).
Biting the hand that feeds IT
