how do you wire a alarm scanner

does anyone how do you wire those alarm scanners so they go on when you shut off your car?

for me, and my varad scanners, i just followed the directions for install. 3 wire hookup, power, ground and the third went to something that went ground when the alarm was armed, in my case, one of the wires for my alarm. if i didn't have an alarm, it would go to something like the cigarette lighter or ignition which has power when the car is on but goes off when the car turns off.

I had one of those scanners on my old car, and it was wired to the cigarette lighter/adapter plug.