DVPGSR: Don't rely on your alarm going off if a door is opened... I found a very easy way to open my car's door for as long as I like without the alarm going off or having to tamper with anything. It should work on many cars, but it is very easy to do on a 3rd gen Integra. It affects any alarm that does not immediately go off when a door is opened; most alarms either wait a second or give warning chirps while a door is open before going off. My cheap alarm only waits a second before going off, but I was able to sucessfully do this trick on my first try. The ironic thing is that the alarms that give warning chirps (like Viper's) are actually more vulnerable to this.

I don't want help any thieves, so I wont give the details, but let's just say that you shouldn't trust your alarm to go off when a door is opened. The defense to that trick is backup intrusions sensors. I think one of those interior motion (aka field) sensors should work.