Last week, Nokia filed to patent technology that will charge your new or refurbished cell phone from the motion of the phone in your hand, pocket, etc. The technology is similar to that of watches that are charged from kinetic energy harvested from the movement of the wrist.
From what I’ve read, the heavier internals of the phone (the battery, transmitter, etc.) will sit on a pair of rails, allowing it to slide up and down as the user moves. That energy is then collected and sent into the battery.
Kinetically charged phones should be great for people constantly on the go. Might not be worth it if you’ve got a desk job though.
More at New Scientist