Here’s a video from Linear Technology describing how to power microcontroller systems with Piezoelectric energy harvesting power supply IC LTC3588-1. It incorporates a full bridge rectifier, and a switch-mode regulator into one IC.

New developments in ultralow power microcontrollers with their high level of integration are enabling monitoring systems which draw sub milliwatts of power. Various energy sources that were not useful as power sources for electronic sensors can now be used.