I’ve heard this story in various forms over the past few years, but according to the London Times, pedestrian power is ready to be harnessed:
Underfloor generators, powered by “heel strike” and designed by British engineers, may soon be installed in supermarkets and railway stations.
The technology could use the footsteps of pedestrians to power thousands of lightbulbs at shopping centres. It works by using the pressure of feet on the floor to compress pads underneath, driving fluid through mini-turbines that then generate electricity, which is stored in a battery.
Apparently, this technology can also be used to harness power from anything that regularly moves due to environmental factors: train & car bridges, antennas, buildings, etc.