I've read about some products which use the energy generated by converting the mechanical energy of a button press into electrical energy. At least in their case, it turns out to be enough energy to send at least a few packets. Even Home Depot sells one! ( http://www.homedepot.com/p/Leviton-Self-Powered-Wireless-Push-On-Off-Remote-Rocker-Switch-White-120-WSS0S-D0W/206365259?cm_mmc=Shopping%7cTHD%7cG%7c0%7cG-BASE-PLA-D27E-Electrical%7c&gclid=Cj0KEQjw2fLGBRDopP-vg7PLgvsBEiQAUOnIXP0td6INXggTpOeOkiv7VOZ2jKVtEpet3Zvk5u-5VUsaAoPF8P8HAQ&gclsrc=aw.ds ), which I believe may be based on or in some way related to Enocean's earlier R&D into the topic.
Anyone tried powering a Moteino for a brief while using a piezo button? What would be a good energy producing button/switch to try it with?