I think it depends on what your goal and expectation for this system is. Something you'd have for "monitoring" the home - heat, lights, maybe a camera here and there would be different I think than something for home invasion and asset protection.
The problem I see with intrusion detection is that it's after the fact. Despite how quickly an alarm company may contact authorities, by the time they may respond the damage is done and property compromised. I've had two neighbors broken into in the last 20 or so years where the alarm functioned properly but by the time the police responded the deed was done, one of them having lost an entire gun safe they had time to pry off the wall and haul out on a hand truck. In ABQ (see DonTom's post on crime here) the response to residential alarms is pitiful, having the lowest priority in their service call queue. Their response to property crime here is to go to a substation to fill out a report, then make an insurance claim. So the idea of having an alarm to protect property is a lost cause and not something I would bother with unless I enlisted the services of a security company. Money would be better spent on motion lights, better locks and securing valuables. Monitoring the home is another question, I have a couple Ring cameras and when those go off we can look and see what's going on. Those would easily be defeated by an average thief but that's not why I have them. The best security/fallback I have is neighbors that I can call from anywhere and have them check on the place, grab a package off the porch or do whatever. I get that's not a plan everyone can use but in the few times there's been trouble on my street the neighbors were first on the scene long before the cops. Not related to alarms directly but something I do when leaving the house for a while is to shut the water off at the street. Having had the joy of cleaning up after a busted wash machine hose even though it happened when we were home I don't want to think what would happen if that ran for hours or even days. There are alarm sensors and main shutoffs that can do this automatically but it's a simple and quick thing to do, and eliminates all doubt.
Mark B.
Albuquerque, NM