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Just how much energy can you make while walking anyway? From google I found this gem. Add it to your collection. Site Reference : http://physicsweb.org/articles/news/9/9/6/1/0509061

and

http://physicsweb.org/articles/news/9/9/6

The “Suspended-load” back-pack. The pack frame is fixed to the body, but the load compartment is suspended with springs from the frame. During walking, the load compartment rides up and down. To generate electricity, Rome and colleagues attached a green toothed rack to the “load plate” of the back-pack. When this toothed rack moved up and down during walking, it meshed with a gear mounted on a generator which generated electricity (Image: Science)

[...] a back-pack that converts the up and down motion of walking into electricity. The device can generate 7.4 watts and could be used by field scientists, aid workers and soldiers to power mobile phones, GPS instruments and other devices without having to carry heavy replacement batteries (Science 309 1725)