Viper (maker of car alarms and remote starters) sent me a PR kit for a new system which will allow you to remote start your car with your Apple iphone.
It looks neat, because you can start your car even if it isn't within direct line-of-sight; the system communicates between the iphone and the car over the cellular network.
However, there are a couple of things I wonder about. First, the cost: after the first year, it costs $30/year for service. Is that worth it? Not to me, when I can have a service-fee free line-of-sight remote starter.
Secondly, I wonder about the safety implications of being able to remote start your car without being near it. All remote starters have a cut-off timer which kills the engine if you don't come and open the car within a certain amount of time, typically about 10 minutes. But without being able to see your car, you have no idea if there is some unsafe situation where you wouldn't want to be starting a car.