Scary thinking about the fact that if there is a billing dispute or anything to that nature, for connected cars in the near future, someone could just turn a car off at whim for a driver. I would hope there is a high regulatory wall formed in the years to come if you want to disable a person's car remotely.
There's something like this already for used car dealerships who lease to high risk customers. A device is installed with a keypad in the compartment. The dealer programs it with a payment schedule and a time. Each time you make your payment, you get a new code and punch it in. If you fail to make a payment on time, car won't start. Some of them even have GPS to assist with reposession.. scary little devices.
When you realise that you can just send commands to a car and get it to do things, the possibilities you can think up are incredible