you would need to use an optical to coax audio adapter.  and then it still would only work if there was actually audio coming from that connector with the tv on.  if the tv volume is turned down, or you are routing audio through an a/v amp, then i dont see this working for you.

i won't do a system anymore without a voltage sensor/xantech current sensor setup when using a TV with a long delay.  it makes it so much easier for the customer to use when the remote knows if the tv is on or not.  it does seem like alot of extra equipment, but once you unbox everything it really isnt that bad.  It would be nice if Xantech would just group all the pieces together and sell it under one part number though.