Human generated electricity

Biological researcher have found out that a human with a 20-20 kg backpack can generate atleast 7-8 watt of power as he/she walk. you know what can we do with it "we can simultaneously power an MP3 player, a PDA, night vision goggles (or 3 LED headlamp), a handheld GPS, a CMOS image decoder, a GSM terminal in talk mode, and Bluetooth". check this link for further details http://www.scienceblog.com/cms/node/8874/