How to Detect Sleeping Mac

I've decided I want to make a very simple arduino device to switch my speakers on and off automatically. I bought some 120VAC relays that are switched with 5VDC. I would like to set up the arduino to detect whether my Mac Pro is either awake or asleep and switch the relay on or off. Does anyone know what would be the best way to get the arduino to detect what state the Mac is in?

Does the Mac shut off power on the USB 5v lines when it goes to sleep?

My Ubuntu netbook does, except when I have a 7-port USB hub connected in which case it won't go to sleep.

...R

gretsch27:
I’ve decided I want to make a very simple arduino device to switch my speakers on and off automatically. I bought some 120VAC relays that are switched with 5VDC. I would like to set up the arduino to detect whether my Mac Pro is either awake or asleep and switch the relay on or off. Does anyone know what would be the best way to get the arduino to detect what state the Mac is in?

i can’t think right know! but a little idea a little app like thing that answers req from your arduino ? like you keep sending every 1 min “are you awake?” if respondd " yes" nothing if no response turn of speaker!!!