Using the same technology that allows hybrid cars to recycle braking energy, Max Donelan invented a gadget that produces power from the human knee - capable of producing 2.5 watts of electricity per leg. The unit is not too practical at the moment, but the technology and potential is sound. Currently the knee power generator weighs in at 3.5 lbs and it looks very awkward to have strapped on. Although 2.5 watts doesn’t seem like too much it is enough to power 5 mobile phones free of charge or resource.