If you've installed alarms, one with a remote start wouldn't be much more work, just more connections. You'll have to tap into the ignition and crank wires, as well the brake pedal switch and tach signal. If you can't find a tach signal wire, directly wiring to an injector at the engine works; sounds like a pain but its fairly simple.
http://engines911.com/asdocs/2W-FM-LED-CMB-A-M(AS-6450)_wd_en_h450s200v100_070801.pdf
Keep in mind that if you have a factory immobilizer that uses RFID key, you'll need to add the appropriate transponder module. As far as I know, these can only be programmed once for a specific vehicle, so beware if you buy used.
I don't know if there's much difference between brands except for range and features, and keyfob prettiness
, as long as its not defective; the quality of the installation will determine the reliability as much as anything. I went with a 2-way combo system from Autostart, no complaints.
If you have any questions, feel free to PM me.[/url]