I've got a Compustar system installed and it works great. Model is 2WFM900AS i think. Alarm and starter combo, 3000 feet range. Expect to pay quite a bit if you decide to go for the 2-way ones. You'll also be charged for a Bypass Module since our cars have the key-microchip security thing.
Basically you've got 1-way and 2-way. 2-way devices will have a way of confirming that the command you sent has been activated (car started, doors unlocked, alarm armed...stuff like that), usually through a screen or a series of beeps. 1-way models wont have a screen and will generally just be a remote with a button or two. The 2-ways will tell you if you're out of range, the 1-ways wont.
Then theres the Starter or Starter/Alarm combo. One is just a starter, the other has a shock sensor and other stuff to set off sirens if someone hits your car or tries something funny.
Then theres range. More range = more money. There are some with a range of 6000 or 10000 feet. I find that 3000 feet is enough for me.
For compustar atleast, you can tell what type it is from the model number.
2WFM900AS
2W = 2way, FM = well FM transmittance, not AM, 900 is the model, AS = Alarm/Starter. Only alarm would be A, only starter would be S.
Hope this helps
FYI, check out Audioheaven.ca. Those guys have lots of stuff like remote starters, audio and tinting. They do a really great job. A lot of Matrix Owners would recommend them.