At no time and in no way should a vehicle ever be connected to the internet. Now, the radio may have some connection to the internet, but it needs to be completely isolated from the rest of the vehicle. In other words, no physical connection to the rest of the vehicle except for the 12V power. If I can unlock my doors with a smartphone, than so can a hacker.
Vehicle to Vehicle communication is okay, provided it is short range and the information sent to each vehicle must obey a standard with all non-standard communications discarded. The information sent must be well-defined and it cannot send commands to other vehicles, just information.
And if I eventually have to buy a car that is connected to the internet, then I would like to see it try working the antenna pulled out. Or with the fuse pulled out.