Some of the features are being mimicked by aftermarket remote starters. For example, my wife's car is equipped with Viper SmartStart. From the phone, I can remotely lock, unlock, start, stop, etc. Higher packages include a GPS module so you can track your car.
However, some of the diagnostic features that GM has implemented are certainly very cool. What GM should do is offer a lower yearly subscription price if you use this feature as it should free up their operators.