True...unplugged....unpowered....the crux of the matter is I have control on the source side of the plug and not the device plugged into the wall.  The device could be a wall wart, a regular plug, so size itself may change thus any sort of optic sense can't be employed but I'd love it I could as it stays away from touching the 110VAC.  Wire wrapped around the hot (or return) would be great if this was a custom one-off or home project but this is going to be a mass produced with as little overhead as possible.
   
  I'm leaning toward the anti-parallel diodes approach, driving a optocoupler. 

"Alan B. Pearce" <A.B.Pearce@rl.ac.uk> wrote:
  >The definition of 'unplugged' is too wide to be useful imho.

Well, the more I read this thread, and the more the OP writes, the further 
my feeling is that rather than "unplugged" he is looking for "empowered", 
and that can be done by simple voltage detection with an opto-isolator. 

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