I had a viper remote start with the smart start system in my Tacoma I had before the dodge. I freaking loved it, it worked great. I hate that I didn't remove it when I got rid of the Toyota so I could put it in my ram. You can lock, unlock, start the engine, shut off the engine, turn on panic mode, and check all kinds of stuff real time like if your doors are closed, hood is open etc all from your phone. You never have to worry about locking your keys in your truck. And there's no range limit. If your phone has signal and your truck is somewhere it has cellular signal, it works.
Only 2 things that I can think of that are negatives. For one, it has a yearly fee since you are basically installing a cellular receiver in your truck. I think it is around 50 or 60 a year. If you get the gps enabled unit that can track your vehicle, it is a little more.
2nd, which wasn't an issue for me but some people don't realize this, it isn't completely instantaneous. It usually takes 3 to 5 seconds for the vehicle to receive the command from your phone. Personally I think this is pretty reasonable for everything that needs to happen to start a vehicle from a cell phone.