The free Viper SmartStart app lets you start your car's engine, pop the trunk, turn on the heat or A/C, and beep the horn, all from your iPhone. The catch: You'll need the a Viper SmartStart system installed in your car, and it ain't cheap.
All your basic functions are present and accounted for: a big circular button on the app's main screen will fire up the engine, lock and unlock the doors, activate you car's security system, sound the horn, and pop the trunk; you can also set the app to crank the heat, defrost the windows, or turn on the air conditioning automatically. Got a garage full of cars? The SmartStart app will manage them each individually.
One of the coolest features on the Viper SmartStart app is that it'll start your car from anywhere, as long as you're in 3G/Wi-Fi range and your car is within Viper's U.S. signal area. So yes, you can start your car remotely from, say, inside a restaurant or the mall, or even from another state (because ... well, you can).
That's the good news; the bad news is that you can't just download the app and start your old Ford Pinto straight away. First, you'll need the proper Viper SmartStart hardware installed in your car, and it'll cost you: think $499 for the complete system if you're starting from scratch, or $299 for a module if you already have a compatible SmartStart system installed. And don't forget the $29/year service plan (at least the first year is free).