Try Fords to see if the "Highguard" option is still available. My wagon is an EF and was optioned with this alarm, it ties in with the smartlock so the original remotes still operate it. Don't know if the highguard incorporates a shock sensor or glass breakage but it is a good general alarm system. Being Ford (if it is still available it might be a bit pricey)
You can also get a Brant system that uses the current keyless remote. It gives you the 3 way immoboliser, internal/external alarm, shock sensor, boot/bonnet protection, makes your morning coffee, etc..
If you want an alarm to hook up to a late model Falcon you can get what is called an upgrade kit. Black Widow make one which keeps your original remote and immobiliser set-up, but also gives you a battery back up siren plus shock sensing and the ability to connect microwave sensors or ultra-sonics if need be. How do I know? I work at Brisbane Car Sound, which is the same as Strathfield down south. About $299 will get the alarm in the car. If you need any info on anything else just ask.
As what chewie said, what you need is whats called an upgrade alarm. My EL came with it when i got it and i wanted to hook up some extra sensors that i had sitting around so i've done a bit research on this. The ford alarm is made by a company called Vision (in Tullamarine), they also sell upgrade alarms and were very helpful when i was trying to find out who made mine.
The alarm that is fitted to my car is made by zenon (in bulleen) these guys weren't so helpful. I think it's good what they do, but to a point. They wouldn't give me any information on the alarm at all (as in wiring diagrams) they said i might go steal cars!! what am i going to do, steal my own car??
I'm looking at a Black Widow 9500S from Strathfield in Sunshine. They quoted me $350. Does this sound reasonable and is this model any good? It's got back up battery siren, shock sensors, boot, bonnet, doors, etc... my only concern is that the wires aren't black in this model (black wires an extra $100). Is there any use in having black wires if you have a back up battery? Won't the siren keep going with the back up battery if these wires are cut?
The Brant alarm seems the way to go, along with all the features Grunter has mentioned it also has a fuel cut off system. Along with my XR8, I also run a 930 Turbo & this set-up features on most Porsches in the clubs & is the alarm set up in demand for fitment to the wrx - to stop the backwards cap brigade taking them 'window shopping' (what else are they good for.) Shannons Insurance will not touch a modified vehicle unless you have the Brant & at $395 installed (with black wiring, 2 key readers & they come to you) you can't complain about the price. Give them a call on 02-9712 5522.