Dave Harper used a trio of Teensy boards to develop a ZigBee based whole-house audio controller.  It’s pretty awesome that he was able to  emulate an expensive commercial amplifier with this DIY project.

The Teensys emulate one of three MDS-6 audio amplifiers, each of which has 6 source inputs and six stereo zone outputs.  The amplifier requires one serial input line and three LED output lines per zone, making the 24 I/O line Teensy a perfect fit.