Some day, researchers hope to enable people to walk to where they need to go. They estimate that the enormous amount of piezo energy generated by 'massively-parallel' walkers could operate more than 10,000 shoe and wind-up toy factories. The story from the PopTech blog:
The R&D team at the East Japan Railway, in collaboration with Keio University, is testing a new system where passenger traffic in the station will be transformed into electricity as a supplementary power source for the station.
The subway turnstiles will be fitted with panels under the floors with a series of piezo electric generators. When a passenger steps through the turnstile, the pressure and vibration of the step will set up a reaction that produces electricity.