I think it could definitely be possible to do locally, and I wouldn't want a car where I have to connect to servers to connect to it. But I am also not sure I want a car that can be opened with a command on the car itself. The code to access your CAR being stored locally on the car itself, with no server side validation, does seem kinda scary. It's one thing for someone to manage to get into your online login where you can change the password, it's another for someone to literally be able to steal your car because they found a vulnerability. It being stored locally would mean people would reverse engineer it, they could potentially install a virus on your car to be able to gain access. Honestly, as a tech guy, I don't trust computers enough to have it control my car.