With the amount of vibration and movement a typical car suspension endures on a drive, you'd think someone would try to harvest that energy with kinetic generators. Whaddya mean MicroGen Systems already did that?
These generators are tiny, just 1sqcm, and constructed of a small silicon flap connected to a piece of piezoelectric material at its base. When the device is disturbed or moved, the flap oscillates and activates the piezoelectric material, which produces current. That current is collected by an equally tiny battery (about the size of a postage stamp) which the entire cantilever assembly sits on. In all, a single device only produces about 200 microwatts of power. However, they're tiny for a reason.
While larger kinetic energy devices often have to be made by hand, these little generators can be built -- cheaply -- using existing chip production hardware. And when combined, they can repurpose enough mechanical energy to, say, power one of those wireless tire pressure monitoring sensors that are now government-mandated on all new vehicles sold in the US.