The Universal Wrist Charger($35) from thinkgeek.
Instead, the Universal Wrist Charger is a rechargeable lithium-ion battery pack with a mini-USB output and 1,500mAh capacity. the charger comes bundled with nine chargers, from the PSP and the DSi to the iPhone and both Nokia adapters. Wristband battery charger will charge your device while you use it! Unfortunately the Universal Wrist Charger has not a motion-powered generator to charge up your its battery from the movements of your wrist.

Buy it HERE