British scientists have built a novel device that converts body movement into electricity capable of powering small gadgets such as GPS trackers. The device, unveiled this week in the July issue of the journal Smart Materials and Structures, is designed to be worn on the knee and harnesses the energy produced by walking. The journal said it could be used by the military to reduce the number of heavy batteries -- each weighing up to 10 kg (20 lb) -- that soldiers carry on foot patrol.
