Well, my wrist watch moves for hour or two during the day, and it lasts for the whole 24-hour day, or more. If a human moves a lot, wrist-watch like cellular phone (cellular connection requires a lot of energy, just like GPS, WiFi, FM radio; remember it) could be viable.

For the best result, all possible energy sources (movements of wrist, hand crank generators, solar panels on your bag/backpack) should be considered.