My GPS, Radar detector, and hidden cell phone charger are all tapped into the radio. These are all low power consumption devices, and it'd be ok. Also, all the stuff turns off when I turn the key off so I don't get to forget it and kill my battery. Another thing it stops me from doing is forgetting to turn the radar detector on when I start driving, it'* automatic.

I tapped mine down by the fuse box because I ran it up the pillar and underneath the vent insert on the dash. You could tap yours directly from behind your radio. I don't think the cigarette lighter is hooked up to the ACC circuit?

Your most reliable way to wire is it to solder and shrinkwrap/electrical tape.

Your cigarette lighter is constant 12 volts. A lot of new cars and trucks have a switched ACC cigarette lighter, or even a constant plug AND a switched plug.