@Chillimonster you could use the 5v on the usb because it kills when you run a shutdown. Even if it is in "standby" and the power isnt fully cut off. Use the usb ground and 5v to power the relay and so when it gets power it flips the relay to turn on your light

My best bet is not to launch EmulationStation until you press that button. Now, how you go about it would require some investigation - I suspect if anyone would have done it, you'd have an answer by now.

Best of luck.

Nothing I know of - and I don't have one of these controllers. I have a real PS3 controller which works well.