I was looking for alarm providers that work with VoIP. Turns out that traditional monitoring companies (like ADT, Brinks) don't really work well with VoIP. I did come across uControl (
http://www.ucontrol.com). They work over broadband and also have an optional cellular channel (and old-school phone line also). They are cheaper and have some pretty cool features like notifications (email, SMS) when the system is armed/disarmed. They have a device that just attaches to my current system. I have had them for a few months. I have been real happy with them.