I thought I would share an article on one of my clients that is developing an energy harvester for military applications. Could definitely see it having a recreational use in the future. http://www.canadianmanufacturing.co...new-kind-of-military-charge-design-eng-104514
It's pretty cool, not as easy to make as you would think. It doesn't really get into it in the article, but the generator actually kicks on and kicks off based on the movement of the leg. Original design/concept was the kineseology professor up at SFU.