As we finish up our build I'm looking for a DIY wireless (not opposed to wired) security system that is expandable. There seems to be a lot of systems out there and many of them will sync with other brand devices. Mainly I'm looking for the following:

- WiFi capable to get alerts on my phone and ability to arm and disarm remotely
- Battery backup
- a couple cameras, maybe expandable
- motion sensor with siren
- ability to add door and window sensors, glass break sensors, etc
- reasonably priced professional 24/7 mointoring capability

Anyone installed anything like this? What do you recommend? I'd prefer to start relatively simple and be able to expand.