Better for the watch form-factor would be the kinetic drive. Plus it gives you an incentive to be more active and the watch can annoy you if you're letting it d

Better for the watch form-factor would be the kinetic drive. Plus it gives you an incentive to be more active and the watch can annoy you if you're letting it die by being sedentary. But both the Citizen-style "eco drive" and the Seiko-style kinetic drive could be baked into the same watch. That's plenty of energy for the deep low power microcontrollers that exist these days, even a fairly powerful ARM-based one. But that's still not enough power to drive the screen on most "smartwatches". Nor their higher power cellular/wifi components. Fact of the matter is, TFT screens eat batteries like no-one's business. No avoiding it. E-ink screens would do better, but have nighttime visibility problems that would be hard to overcome. Plain and simple, the undoing of the smart watch is the battery. It's an obstacle we may someday overcome, but until that day, it's not likely to catch on and become the big hit everyone wants it to be.