Fortunately, Viper lived up to its promise. The company makes a remote car starter called SmartStart, which you can get installed in your car at pretty much any dealer that handles such things (Best Buy is probably the most common, Viper's rep told us). Once that system is installed, which costs you anywhere from US$140 or so up to around $300, depending on your vehicle, the local dealer's costs, and all of the other options, you can use Viper's free SmartStart app to control the unit in your car, which means you can pull up the app and hit buttons to lock or unlock the doors, or start the car.
The app's functionality is rather impressive -- if you get the Bluetooth model starter installed in your car, it only works via Bluetooth of course, but with the official SmartStart model, the app actually works over the Internet, so anywhere you have cell phone service, the app can control and monitor your car. You could be on vacation in Italy, for example, and get a notification when the car alarm goes off, or double check that you locked the doors.
While the app's functionality is very cool, the interface on the app is just plain hideous. I guess that's about as much as we could expect from a car accessory maker, but if they indeed didn't run it by a designer or two, the app would certainly benefit from doing so.
But yes, you can start the car from Siri. To do so, you just say "SmartStart" into Siri, and then the app will automatically load up (as will any app you tell Siri to load), and will run one of three commands: You can choose to have it lock your doors, unlock your doors, or, yes, start your car. The Viper rep set it to start a little model car in the booth, told Siri to "SmartStart," and sure enough, when the app loaded, the little model car roared to life.
Yes, if you don't need a remote starter, picking one up just to do this is probably a bit too expensive. But it's good to know that it's 2013, and if we want to, we can indeed start a car with Siri.