A new energy-capturing knee brace can generate enough electricity from walking to operate a portable GPS locator, a mobile phone, a motorized prosthetic joint or an implanted neurotransmitter, research from the  University of Michigan shows.

The wearable mechanism works much like regenerative braking charges a battery in some hybrid vehicles - Regenerative brakes collect the kinetic energy that would otherwise be dissipated as heat when a car slows down. This knee brace harvests the energy lost when a human brakes the knee after swinging the leg forward to take a step.

The dude needs to sort out his sock/shoe situation however.