The Raspberry Pi  can be used as a radio transmitter… ( http://www.weedpi.com/how-to/create-an-internet-radio-fm-transmitter/ ) – my little RTL sdr usb device can pick up radio transmissions…… now this projects takes those two great tastes and brings them together in order to transmit data over the air and receive it . "Big deal!" you might say in the age of wifi/bluetooth. For some uses though this is a great deal as with very little cost you can make a method to move data around on non obvious frequencies, not to mention encoding methods, such that the big and little brothers might not be able to catch.  Ah, there you go. 
We are going to use a Raspberry Pi as a transmitter and our RTL-SDR setup to decode the signal. Here is a video showing ascii @ 9600bps and 1200bps. Find a Raspberry Pi and set up a Pifm transmitter as described on the Imperial College Robotics Society Wiki page. We will use AFSK and minimodem …
