Instead of just burning calories, why not use all that energy from exercising to power your MP3 player? The Dancepants Kinetic Music Player, a shortlisted entry in Designboom’s Green Life competition, lets you do just that by converting kinetic energy from running, hopping, jumping, etc. into electricity to power an iPod or other music player. According to the Dancepants designers, the product is a “100 percent interactive way to feel the value of energy on your own.”