Rice University engineering students Tyler Wiest, Carlos Armada, Julian Castro and David Morilla have developed a (slightly awkward) foot-powered generator called PediPower. It's functional, and can be used to power a phone or another small portable gadget just by taking a leisurely stroll while wearing the shoe attachment. It's a great incentive to walk around the block more, because every time weight is placed on the heel, energy is sent to a belted battery pack.
The original assignment was to "create a device that could harvest energy from human movement," so PediPower looks pretty good from that standpoint. The team, dubbed the “Agitation Squad,” agree that this activity-driven energy generator is a tad cumbersome, but also that there are tons of improvements that could be made to their initial prototype. So after PediPower's size, weight and overall user experience gets tweaked, the team hopes to use it power something like an artificial heart, which is a use that will certainly encourage people to get out an walk a lot (and never, ever stop).