Wireless has been around in the alarm industry long enough to be pretty much perfected and reliable. So you don't have to worry about the technology at this point. I don't use any of the "self-contained" alarm systems because it's just not my market. I'm usually in the mid to high end installs. I've used Napco alarm systems for over 25 years and when they introduced wireless, I just stuck with them, and have never been disappointed. They've got a good stong signal and penetration seems to equal anything that I've put it up against.
You may get some responses regarding ITI being "the best" however, in my opinion it's simply the most promoted, advertised and marketed. Not that it's inferior in any way, it's just that most of the other top of the line wireless manufacturers started of in the hard wired alarm systems market. So when ITI started it's introduction into the alarm industry, since it was wireless product, in a hardwired world, it had to do some super-duper marketing and advertising. Which it did .... quite successfully. And it could be .... that at one time it was the best wireless, simply because the others weren't competing in that market. Now days, as I say, most of the major players wireless is pretty much equal and ITI is no better or worse.
The primary problem with wireless is that it is thought by many to be a "quick" installation. When, in reality, it may take as long, or longer to install a good, long term, wireless system. Many of the "quicky" "free" system you see/hear about are wireless systems that are installed without any signal checking of proper trial and error placement of transmitters and receivers. In such systems, problems are inevitable, and thus the "bad reputation" of wirless is perpetuated. I've got ....maybe 50 ..... 60 .... 70 totally wireless installations, some with as many as 60 or more transmitters ..... some systems 20 years old and ..... I've never had a call about poor reception or wireless related problems. And every system capable of it, is programed to send reports upon failure. Only the normal calls that could be expected on any installation. So, it's proof enough for me, that if the wireless is installed with the utmost care, there's no difference between it and a hard wired system. By the way, nowdays, battery life expectancy is minimum, 3 years. I've had some go seven years. However, come to think of it, I have run into some "quirky" lithium batteries, that have only lasted a few weeks or months. So you may want to consider that as a "wireless related" problem. I don't.