Endless Energy?

Cnet posted news that MIT undergrads developed a shock absorber that generates electricity. Whenever a car equipped with these absorbers hits a bump, it would generate electricity. This reminded me of an article I read a few years ago, I think in either Times or Newsweek, that mentioned someone working on a backpack for the military that would do something similar. Apparently the modern army can be tracked by following the trail of spent batteries. If a foot-soldiers backpack instead generated electricity, they could charge all of their electronic gear while they marched. The idea wa thtat there would be a device in the backpack that generated electricity by absorbing the impact of a person walking, similar I think to these shock absorbers. Even though this stuff is often first developed by or for military use (I've been told Ray Ban sunglasses and velcro were developed first for the USA Airforce), they can be put to use for many other purposes: imaging charging your laptop by walking across campus.

I know it would take energy and resources to make such things, but the idea of being able to generate usable electricty simply by walking is fascinating. I don't know how much energy it could create, but my sci-fi imaginings conjure ideas of electric cars that would rarely need to be charged by an external source, or being able to charge all of one's personal electronic devices without plugging them into an external source. Capturing electricity from people walking would be as renewable as solar or wind, and perhaps might motivate people to move around a bit more: if walking 30 minutes to work meant saving money on electricity at home, it might just motivate people.

Neat idea. I hope more sci-fi starts using this...