Last year, we built the Drumbot for display and exhibition around Richmond, VA. He is over 7 feet tall on a good day, and plays 4 drums using the Arduino as a brain.
This year, we gave Drumbot a heart, in the form of a home-reengineered PMA-as-generator. Our robot heart puts out a solid 80 volts (AC) when attached to an exercise bike. This is the result.