It's no surprise that the number of labs and companies exploring energy harvesting applications is growing by the day. Think about the endless amount of kinetic energy that's lost during our activities.
The earliest versions of energy harvesting technologies were attached to what was moving and creating impact: people. You've probably heard of designs that can capture energy from walking (attached to shoes, knees, or backpacks) and then produce electricity to power portable devices like phones, ipods, or military communications equipment. The efficiency of portable electronic devices is improving, making energy harvesting technologies all the more useful and practical.
Hybrid vehicles use an energy harvesting technology to get power from braking, though I'm surprised the cars still don't use this kind of piezoelectric technology for getting electricity from the wheels, shocks, and engine vibrations. After braking energy, these seem like the next biggest sources to tap.
Energy harvesting designs have also expanded to experimental applications for impacted sufaces, like stairs and walkways. In London and Tokyo, there are pilot projeccts that harvest the energy created by people walking on subway steps and platforms and then power the subway's lights and PA systems.