Image: Lightning Packs
Lightning Packs is a company that is developing backpacks that generate electricity with the motion of their users. As the user walks, the spring-mounted backback bounces slightly, turning a gear on a generator. It is the brainchild of Lawrence C. Rome of the University of Pennsylvania, who hopes to market his idea to the U.S. military:
"Soldiers now carry GPS receivers, night vision goggles, headlamps, communication devices, and more. And with this technology, means of powering them becomes critical. Soldiers carry eighty pound backpacks, up to twenty pounds of which are spare batteries. Now, with the Suspended Load Backpack, electricity can be generated to power the equipment directly or to charge a lightweight rechargeable battery," Dr. Rome said.
When walking, the Suspended Load Backpack can generate up to 7.4 watts, more than enough power to simultaneously power an MP3 player, night vision goggles (or 3 LED headlamp), a PDA, a CMOS image decoder, a handheld GPS, Bluetooth, and a GSM terminal in talk mode.
Link via Gizmodo (where there's a video)