I would think that considerable energy savings could be achieved by having the device active only when the user is engaging with it. Much of the time the device could be in a sleeping mode awaiting incoming data or user input. If the device isn't being worn, it could be in an even deeper sleep mode. Still, there needs to be a recharging plan. Will the devices operate on a long life battery (like an electric watch) or will they have some mechanism to recharge overnight when not in use like a cell phone?
Very good point @_hm...but how do we tap to the energu we consume via food?...I remember readng about glucose harvesters, but by definition they need to get implanted somewhere in your body and get the energy out from there, not a pleasant solution even if it works...the most simple is to tap to the temperature difference between the body and environment but this only works in cold climate or air conditioned rooms...Kris
No reason why movement/kinetic energy cannot replace a battery, or keep a battery or supercap charged. Your point is valid, I was agreeing with you. But also pointing out that such energy harvesting is a proven technology that has been used for a long time and therefore would most certainly be viable in today's applications.