You will have seen over the past year or 2, kids rolling around on their sports shoes. They are basically regular sneakers but with a roller in the back allowing kids to slide around rather then walk. These latest custom built versions feature a small generator built in which can harvest the power from rolling around. I guess it would be good for powering an iPod or mobile phone in an emergency although I cannot say how much harder it would make it to skate around with the generator kicking in.
Via: TheDailyInvention