Run a script when Steam Streaming starts

Question

I'm using Steam in-home streaming from my desktop PC to my living room. The only problem is, my monitor and my living room screen have different resolutions, so every time I switch I need to change the output resolution, and I'd like to stop doing it manually.

I've found some options for changing screen resolution with a script, now I just need a way to run a script when Steam Streaming starts. Streaming is initiated from the remote device, so I need to be able to detect when streaming starts, then run the script.