I grabbed several split core current sensors off eBay and have been gradually deploying them. This week, I added current sensors to the family room TV, amp and DVD player. Now, when the DVD player is turned on, the system checks if the TV is on. If it isn't, it sends IR to turn it on. Then, it turns the TV volume all the way down since audio will be piped through the amp. Next, it checks if the amp is on and powers that up if it needs to and sets its input to DVD.
Update: I have taken all these current sensors off their DS10A's and ran Cat-5 to the gameport controller I use as a contact closure device.