my view on car alarm is bit mixed, any old thief can get it installed and then reverse install it just to see where all the wires are connected, but doing your own kill switch means that only you know what you did to the car, unless someone has put one in already in which case you'd want to change the location in case the guy is crook. Having an alarm does make it harder for the average thief to steal but then again, so does having a home make kill switch.