I knew someone had to have invented it...

  "This is the Forever Flashlight from Excalibur Electronics. It uses a "wobble" generator (basically a bar magnet moving back and forth in a wire coil) to convert the energy generated by physically shaking the flashlight into electricity to generate light. This is not a new idea; wind-up dynamo-driven hand-held appliances such as the Freeplay Radio have been widely marketed since the Y2K scare. The cool thing about the Forever Flashlight, and others like it is that it uses one of the new super-bright LEDs as a light source, which means that, not only does it never require batteries, it never requires replacement bulbs. No part of the unit is openable; the case is injection-molded around the components. It is thus entirely water- and corrosion-proof. You could bury it in a swamp (or a bomb shelter) for 20 years, and still count on it to light up after a vigorous shaking. Because LEDs convert electricity to light so efficiently, 30 seconds of shaking can provide 5 minutes of continuous light. I keep mine in the windowsill; if there's ever a power-out, what light there is will be coming through the windows, making them, and thus the flashlight, relatively easy to find in the dark."

You can find it and other wonderful inventions here.

I want it...