From Scientific American:
Scientists have developed a backpack that makes “power walking” a reality. Described today in the journal Science, the novel device translates the regular up and down movement of a walker’s hips into electrical energy. The contraption could conceivably help provide power to soldiers, relief workers, scientists and others on remote trips. When out for a stroll, a person’s hips move up and down between five and seven centimeters during every step. Larry Rome of the University of Pennsylvania and his colleagues exploited this trait to design their new “suspended load” backpack. The bag is based around a frame, which is connected to a wearer’s hips, and as the frame gets raised and lowered, the backpack’s contents move up and down.
More here.