Another bit of prior work was Tempest For Eliza [1], which generated patterns on old CRT screens to play music (arbitrary MP3 files!) on nearby AM radios.
Edit: And here's another one that transmits data over radio by toggling GPIO pins and the UART on a cheap laser printer: http://www.funtenna.org/
Edit: And here's another one that transmits data over radio by toggling GPIO pins and the UART on a cheap laser printer: http://www.funtenna.org/
[1] http://www.erikyyy.de/tempest/