Power On PC on BT Controller Connection

[Nold360]

I had the idea to use this code to implement a "simple" hardware level "PC Remote power on" (like for consoles) for my DIY "Steam Machine" by using a transistor or octocoppler to power on the PC.

Currently i have two questions:

1. What would be the best point to implement it? is it a service? i don't want to implement it in the "apps" since i guess it would be best to have this feature available in different build targets, too. My first guess would be a bluetooth callback, but i'm not sure how to implement that at this point.
2. Which pins are still free to use? I would need two, one for Output and one to detect if the PC is already on