Jeff
I do something similar … but the opposite!
I setup a water sensor across a relay that tells me when there is NO power in a socket.
You could just use the same setup but showing when power IS present.
Cut the end off the water sensor cable and connect a relay between the two cables that go to the sensor
I power the 5v relay with a simple USB charger
You can easily modify the DTH to show something nicer than wet/dry on the 'things ’ page as I did
Let me know if you need any more details and I’ll try and write something up
I originally used expensive Fibaro door/window sensors… but you can do exactly the same with cheaper wet/dry sensors
Have a look here
Andy