Brainstorming - Detect if "dumb" AC is on

It all depends on how “invasive” and “handy” you are. Assuming there is a control pannel on the wall with a LED indicating the status of the device, I see two possible options:

  1. set a light sensor (photoresistor) on the top of the LED to read its status and then send a signal via a 433MHz device, e.g. this one. The con of this option is that you are to loose visibility on the led.
  2. Open the device and connect two wires to the led so its signal is to drive the 433MHz transmitter.

Thanks for all the ideas.
I will try to look behind the panel but I doubt there will be room in there to place a sonoff though.
Will see if maybe I can make it work with watching the led otherwise.