Thought this was interesting. Could be handy in a zombie apocalypse or some networked sensors or something.
http://hackaday.com/2014/08/15/bluetooth-low-energy-beacons-in-a-flock-of-birds/Although much simpler things exist. A hand full of transistors and enough wire for antenna and shit, it could be done way cheaper and maybe more efficiently with comparators and simple opamps working on a radio band doing something similar to spi or something, but that is my opinion..
