cheap wireless communication

Ian, that was too funny!

The sparkfun Rx/Tx works well, easy to program to send a message from the Tx to the Rx using virtualwire:

See the "simple remote for granny" to make the Tx side sleep in between transmissions if you want it battery operated, build it around a 3.3V ardweeny & power it with a 3.7V LiPO battery, recharge it once a month or so. Or 3 AAs will also work. Bring power direct to VCC pin, no regulator to suck your battery down.
http://www.solarbotics.com/products/kardw
(click resources, manual, easy to assemble)

On the Rx side, search the Tone tutorial, make it play whatever song you want thru a little speaker (or an amp and a bigger speaker) when you get a message in.

<$30 in hardware, mount both sides on some perfboard.