Hmmm good point... Anyone here actually set up a GPS tracker on theirs?
I have setup one of those cheap GPS trackers in an old car of mine, for reference it cost about $30 for the tracker + $10 for a SIM card with credit.
Was easy to install and use, however they only suit daily drivers.
If I left the car parked for anything more than a week it would drain the battery to the point it wouldn't start. I wired it up to a switch so I could turn it on when it was parked up away from home, but it was too much of a hassle and easy to forget.
In my experience car alarms or neither a deterrent or added security. Might as well install a flashing LED on a switch.
For cars that don't get driven often I would recommend removing parts, i.e. quick release steering wheel, ECU, ignition, fuses etc.
For cars that get driven at least once a week, try the GPS tracker + hidden kill switches.