There are a few threads discussing remote starts.
Best combo to go with is a model like the Viper 5104 with basic remotes. Expensive remotes are a waste of money, especially if you are getting a Smart Start module. Have the installer (and you need an excellent installer, can't stress this enough) program the Viper system to work with your factory key fobs so you do not have to carry two remotes since you will always need to carry your factory key fob anyway. The major difference between Viper System models is the remotes buttons/screens and the claim that some have more range than others. If you program your factory key fob to work with the Viper, you will only have to carry one remote and you can use your phone to start the car if you feel like your ever in a position where you need more range.
This is the set up I have and I love it. I definitely recommend the Smart Start. It comes in handy when you are too far to use the remote, which is more often than you may think like at work, or in the movies, out at dinner, at the mall, I could go on forever. In the winter the car gets warmed up nicely before I am anywhere near it, hop in and go.