Well for a suitably frugal definition of "useful", you can. See their whitepaper: http://getfreevolt.com/downloads/RF%20Energy%20Harvesting%20Whitepaper.pdf htt

Well for a suitably frugal definition of "useful", you can. See their whitepaper: http://getfreevolt.com/downloads/RF%20Energy%20Harvesting%20Whitepaper.pdf http://getfreevolt.com/downloads/RF%20Energy%20Harvesting%20... Any EE experts around, willing to validate their assessments?