This guy turned his Pi into an FM transmitter by modulating data onto one of the GPIO pins and using a piece of wire as an antenna plugged into it.<br><br><a href="http://hackaday.com/2012/12/10/transmit-fm-using-raspberry-pi-and-no-additional-hardware/">http://hackaday.com/2012/12/10/transmit-fm-using-raspberry-pi-and-no-additional-hardware/</a><br>