I have owned 5 Jeep wranglers. I have had only one alarm. The one I had a high end stereo system and top of line alarm with motion/proximity sensor. It worked well nothing was ever stolen. I moved to SLC's red light district for a while. The first night I lived there it was 3 am and I was sound a sleep just 10 feet from my jeep that was parked under a large light and out of site off the street behind my house. The alarm goes off. I get up and run out with my gun... nothing. The next night same thing. The third night same thing but this time I caught the burglar. It was a fat Siamese cat sitting in the front seat. Mostly it was just a pita. It would go off in the wind. The weather would change the sensitivity and its zone would grow or shrink based upon temperature.
I have had stuff stolen out of my jeeps but mostly it was just petty crimes of opportunity. Clothes left on the seat... Screw drivers, wrenches etc and some used tennis shoes. I even had $20 in change stolen. I usually n just keep my car open with nothing of value in it. It is well insured and I have a nice security trunk for the really valuables that occasionally need to be in the car.
This seems to work for me but I must admit I have only been a victim of crime in Utah.. Not 20 years I spent in CA, or 2 years in Boston, or 5 years in the Carolinas.