Personal Energy Generator
The nPower PEG, an acronym that means "personal energy generator," harnesses the energy generated as a person moves about and transfers it into a free, modest power source for electronic devices. The user carries the device in his or her pocket while walking around or exercising. Within the wand-shaped device, a weight jostles around to generate electricity in a series of coils to charge an internal battery. A port on the nPower PEG allows the user to connect to and charge personal electronics devices like cell phones or MP3 players.
It's a modest amount of energy, and the exchange rate isn't consistent. It takes about 26 minutes of walking to generate enough energy for the nPower PEG to generate one minute of phone time on a 3G mobile phone, but it can generate a minute of power for an iPod Nano with every minute of walking (more vigorous exercises like running create more energy, of course) [source: nPower PEG]. And while the energy it generates is free, the technology is not -- it retails for $159.99 from the manufacturer.