Muzak uses a Pentium PC, a Matrix Orbital LCD display and an IRman infrared receiver, plus lots of miscellaneous cables and extras.
This infrared receiver costs about $40. It interfaces directly to the serial port on a PC. The company that sells them (Evation) also has drivers on their web page for using IRman with windows. You can use any remote control to control things like winamp and powerpoint presentations. There were no drivers available under Linux, but it turns out to be just a matter of reading in characters from the serial port.
The Matrix Oribital 20x4 display makes development a lot easier. It has a built in RS-232 connector, and it can be powered, written to and read with just 4 wires. It also has a backlight and has built in support for graphs and big characters. The main drawback is that it costs US $75. I would like to make the system work with a cheaper display. One potential source of a good driver for a cheap display is LCDproc.
Voltage: 8-16 VDC