I’m sure that most of you have used hand-cranked generators in science class, so why not actually take it out of the inapplicable classroom and apply that science to charging your mobile devices?
This is what the RollerGen bike mounted generator is designed to do. As you pedal along, all the energy you burn gets put in a battery that resembles a bar of soap.
Of course, this costs about $495 for this system, which is pretty steep.








