tssdetailing said:
so if i break in, and am fast enough to pull out the wall plug-do i win?
Well, if you smashed up the entire system or went wire-cutting, yes, you'd silence the physical siren that would be wailing. However, the second the alarm goes off, it sends a message to my monitoring company, who sends me an e-mail to my BlackBerry as well as calls me. So, while yes, you could silence the alarm pysically in the shop, I would have gotten the notification by then. Even if you find and cut the telephone wires before breaking into the building, I'd get a "loss of connection" notification, which is usually pretty self-explanitory unless you don't pay your phone bills
You can get really fancy too by installing back-up communication devices that run over GSM cellular networks, so if someone cuts your physical landline phone line, the cellular back-up takes over and keeps transmitting information.
There are other benefits to these systems too. For example, you can install monitored smoke detectors and flood sensors, so if something starts burning or leaking, you'd get notified as well. You can also set it up so you receive notifications when the system is armed / disarmed. For example, all our employees have unique arming / disarming codes, so when they either open in the morning or close at night, you'd receive a notification letting you know who armed or disarmed the system. Nice thing about that is when you get a notification that the system was disarmed at 8:21am, and your shop is supposed to be open at 8:00am, you can start asking questions should you happen to not be there that day

Plus there's security against employee time-theft, blah blah blah.
The advantages to these systems go so much further than simply protecting against break-ins.