Uses standard sound cards. Nifty: http://stevetarzia.com/sonar/

Also check out his low cost 16 core workstation. He's using 4x Opterons with Xigmatek coolers.

Looks interesting.

I've tried getting something simular myself. Wrote a small .bat file which switched the monitors on and off using motion detection from my webcam and the software webcamxp.

In theory all this stuff is great, but in practice my motion detection idea used lots of CPU cycles, which put energy usage up on the machine. Although probably less than the amount my monitors use.

It's quite possible sonar would reduce the amount of energy needed. Thanks for highlighting it!

Would this actually be much easier than having an easy to hit button that does it?