House came prewired with a system that I added additional sensors to. I use the local alarm functions only (even though it has the capability to dial a monitoring service). I added a plug-in box that auto-dials my cell phone if the alarm ever goes off (essentially it allows me to act as my own monitoring service). I can remote log-in to my cameras to look around and decide whether or not I need to call anyone.
Monitoring services are a rip-off IMHO.
2 Channel Automatic Telephone / Pager Voice Dialer, USP AD-2001
You will NEVER break even on cost savings on your homeowners insurance either. I shopped probably two dozen and the best deal was a 20% discount. It didn't matter what if any monitoring service you had either. YMMV