This just in...
Knee-mounted device capable of producing about five watts of power
Last Updated: Thursday, February 7, 2008 | 2:34 PM ET
CBC News
A group of Canadian and U.S. scientists have put a twist on the term "power-walking," building a knee-mounted device they say can harvest enough energy from a person's stride to power multiple cellphones.
http://www.cbc.ca/technology/story/2008/02/07/tech-knee-energy.html