Aside from what's in the box, you'll need at least 1 good roll of 16 AWG wire, a few relays, a few diodes, a soldering iron (I recommend the battery powered ones, but NOT the cold heat ones!), plenty of solder, and patience. Oh, and like the other 2 said, you'll need some comfort in working with electronics.
If you want a lifetime warranty on the work, go to Best Buy. They charged me $99 for the alarm install (it was a Viper 791XV) and they didn't enable the remote start, so I did that myself.