Piezoelectric tiles aren't just for dance floors, though. Similar devices have been installed at the London Olympics site and are being prepared for use in shopping malls so that the foot traffic of shoppers can be harnessed to power half of their lighting needs. Also, the tiles light up when stepped on, reminding pedestrians that their plodding footsteps are actually contributing to something other than moving them from one tepid plane of existence to the next.
As demonstrated by Steve Martin.
According to DARPA (the mad scientists who design futuristic devices for the U.S. military), the energy generated by your walking, nodding and breathing will one day power all sorts of sci-fi crap they're planning on sticking all over your body, like computer screens in contact lenses. We tried to figure out how that would work by pressing our computer screens directly against our eyeballs, so we assume they still have some bugs to work out.
With this technology and legalized Ecstasy we could solve the energy crisis overnight.