you need to figure out what you're overall goals are in this security system you are seacrching for, some examples being:

-auxilary inputs (allowing to turn on stereo by remote, turn on neons, things of that nature)
-door lock/unlock
-interior/exterior proximity sensor (basically a bubble or shield around and inside the car)
-windows roll up/down
-trunk pop
-remote start (either automatic or manual, both can be legally and safely done)
-any other things

figure those out and get back to us