Andrew,
I have the AutoPage RS-650Plus which includes a two-way pager (so you can see visually what is giong on with your vehicle at your keychain), the siren, the dual-range vibration sensor, a glass sensor, and the brains, of course. A remote start module is also included with the RS-650 Plus package, and it is definitely worth it. I had it professionally installed due to the fact that it messes with a lot of ignition wires, etc. However, if you were to do this yourself, I'd advise (HIGHLY) having a wiring manual by your side. There is nothing I attempt to rig up on my Trac without that manual.
Anyhow, the one feature that really comes in handy with the Autopage is that it tells you when your battery is being drained. Not sure if others do this. But just this morning, I walked outside and it was diong its thing. Sure enough, I had left on one of my switches for an accessory which pulls a good bit of current. It did its job and let me know. (Of course, the battery would have probably been drained by now because it was going off all night apparently. I have a lot of emergency lighting on my truck, so I installed a PriorityStart module - $89.00 from batterymart.com - and it cuts off any draw from the battery if the voltage at the battery drops below 11.4V.)
Good luck. Hope I can help with any questions. Email me for a quicker reply!
LB