I have been using x10 alarm systems for a tad over 15 years on various properties, houses, out buildings, etc... they are quick and dirty and cheap. They work. The problems that I have encountered with them is the instructions are poor at best. They are not logical. Once you figure them out, its a piece of cake. And the wireless door/window sensors that used to use 9V batteries went dead every 9 months or so. The newer sensors that use the AAA batteries seem to last longer. The oldest one I have is about 12 years old. The new sensors work with the older systems, once you figure out what is similar on both systems. For a hundred bucks, it does what it says. But I'd invest in better, louder, outdoor sirens. Indoor sirens are not going to attract much outside attention. That's what you want.
The first thing I'd do if I was breaking into a house is to cut the phone lines, so don't rely on the autodialer on a wired phone system. Rely on the loudest siren you can get to alert the neighbors and scare the intruders. THAT is the best first defense in my opinion.
