Why not simply have that option in the car? This is all those fancy new cars with video displays, right? You just get an option that says, "There are updates available for this vehicle." Just like most software these days.
I wouldn't want this tied to smartphones, because many people do not have them. My next car will probably have some of these new 'features' , because you won't be able to buy a car without them. But I don't have a smart phone anymore, and I won't be getting one.