On my old sound off car, I used a Viper alarm. Dbl. hood, trunk, door sensors. glass breakage sensor, interior prox sensor. Brain hidden up in the top center of dash. Dummy brain above column wired into the real alarm. Dbl battery back up, two sirens up front, two inside the car, two in the back, all on relays, all 120db sirens. diodes on all external lighting circuits. It had 4 attempts on it, that I know of, none successful ...
Now for my truck, I have an AR,12ga, and a .22. 2 air rifles and a crossbow, a german shephard, and 2 mutts. 11.5 acres back in the woods. (my drive is a 1/4 mi long)And a tractor with a 6'x18" post hole digger .....
And everything in my truck is bolted through the floor, and hidden. If you looked in it, you wouldn't know it even had a system in it ...
Hell, if you looked at my truck, you wouldn't even expect it to have a stereo in it ...LOL...