Despite the announcement that "on the CES floor, they were able to charge a BlackBerry from 30% to full in about 90 minutes, using nothing but ambient WiFi signals as a power source. " [1]
The device has never been turned into a commercial product. [2]
[1] http://www.ohgizmo.com/2010/01/09/ces2010-rca-airnergy-charg...
[2] http://www.ohgizmo.com/2011/01/07/ces-2011-hey-rca-hows-that...
http://www.creative-science.org.uk/mobile_LED.html
Of course, that's a tiny amount of power but it's still there to be harvested.
Not sure what the legal situation is. In England an "artist" was asked to remove their installation of flourescent tubes in a field below power lines. They similarly harvested power. (I can't find that case using Google :-( but here are plenty of others https://www.google.co.uk/search?q=fluorescent+tubes+power+li... )
RF energy harvesting is a bit of a hot topic, there are a number of modules on the market atm. Just search for it on mouser or farnell to get started.
Thanks btw for that LED schematic, so simple. I'm currently tuning a harvester around a BQ25504 and super caps. I'll give it a test next week.
http://uk.mouser.com/Embedded-Solutions/Energy-Harvesting-Mo...
This one contains other energy sources as well:
http://uk.farnell.com/jsp/search/browse.jsp?N=2002+225290&Nt...
He just sat in silence. Eventually he was successfully prosecuted for "Theft of Electricity" from the places he had placed unauthorised phone calls through.