If you're going to harvest energy out of thin air, from vibrations, or from every. single. drop. of battery juice, why not go mad with power and use this thing? Using e-peas's battery-squeezing, electron-capturing IC - The AEM30940 - the Insanity Harvester should be able to extract energy from FM broadcast signals or squeeze a AA battery until it's dry. This thing pretty much just exists to see what is possible with energy harvesting because this might end up actually having practical uses other than being a huge waste of time.

I actually haven't tested it yet lol because I don't have the boards. So I'm not sure if it can harvest broadcast FM signals, but maybe it can. If it can't then this should be able to still power a sensor with a tiny solar cell or piezoelectric harvester. If all else fails, then this is one of the world's best joule thieves.