Anti-Theft Suggestions.

I had a convertible that I wired one of those Motorola radio's into the interior light system in the car and put it in the radio in the glovebox with the call button taped down.
The other radio was next to my bed on a charging unit and I would turn it on at night.

I left the car unlocked because it was a vert and I didn't want the top destroyed because some jerk want my tach off the dash.
I didn't have interior light bulbs in it, so if you opened the door there was no lights or anything but you sure knew someone just opened your door because the call on the radio would go off.

You knew, but they didn't know you knew.