Power-Generating Shoe

A new power-generating shoe that takes advantage of bubbles and able to efficiently harness human motion for energy. The bubbler is able to draw on low-frequency energy sources, such as human motion, by creating tiny bubbles at a high speed resulting in the high frequency needed for efficient energy conversion, with a proof-of-concept device able to generate about 10 watts per square meter.

http://news.wisc.edu/power-walk-footsteps-could-charge-mobile-electronics/