Your question reads as if you want your own backend system. There are some old school systems that call you on the phone you programmed is so that's the backend system.

The Perfect system you noted has the backend at that company so you pay for that monthly.

The key word here is MONITORING. We really don't need that if the system can call us or we can check on it over the web.

Read more at https://www.google.com/search?q=diy+home+security+without+monthly+fees