Two interesting bits to look at, omxplayer and fm transmission direct from clocks on Pi board

The Pi board can be set up to do FM broadcasts and an example is here:

http://makezine.com/projects/raspberry-pirate-radio/

Another article mentioned a media player that can be used when on the Pi in text mode, omxplayer

Also here is essentially an Arduino Uno which lives on the top of a Pi GPIO.

https://www.youtube.com/watch?v=GBeTOGnuUMM

board purchase / support site is here:

http://www.dawnrobotics.co.uk/pi-co-op-raspberry-pi-arduino-add-on-board/

£16.99, obviously from UK.