It would be reasonable if what that app did was anything that actually needed internet servers to work. Why not just pair up the phone with the car, ad-hoc like you could with a PSP, or any sort of peer-to-peer between car-phone, and call it a day? Oh, right, because then you can’t create a service you can charge monthly for.
That people are willing to pay for effectively a remote temperature control and shutdown timer, that does not need to be an internet service to work properly, can and should be dunked on.