This thermometer, the RMR500 Eco Clima Control, of the Australian Oregon Scientific can work for three months in a row after charging in sunlight. Available in the spring for US$99.
Future Vision by Erwin Van Lun on this article
We’ll start to see more and more products that can take care of themselves: connect to networks on their own, power themselves, so that we can take it easy (not so much to save power, that’s not our motivation). This kind of devices (and then maybe not a thermometer) will conquer the third world, where there’s no lack of sunshine but of good electricity facilities, rapidly.