I've been shopping around as well, but I need a system that doesn't rely on a phone line, since I have no intention of ever paying for one. I don't have VoIP either, just cell phones. Some companies offer a wireless alarm system, but they are expensive. I searched around for internet-based monitoring, and found a company called
NextAlarm that not only supports it, but is also quite inexpensive:
Without a contract it costs about $22.18/month (converted to Canadian).
A 1-year contract is $18.47/month, and a 3-year is only $14.76/month.
Unlike most contracts, the only fee you pay to get out of it is that they will treat your account as if it had a shorter contract (or none if less than 1 year) and charge you the difference. E.g. you buy a 3-year contract for $531 but cancel after 14 months, then it's like you had a 1-year contract ($222) and two monthly bills ($44), and thus you will be refunded $265.
The best part is that you can track everything online. A full log of all your activities, including arm/disarm reports, test signals, etc can be viewed online and you can even set up electronic notifications via email, text message, or pager.
It seems like there is a catch somewhere... but I've done some research and found user reviews of NextAlarm, and there were very few complaints. So I'm going to try them out, as soon as I get my house wired properly, or install a wireless bridge next to the alarm box.