Putting the hacking out of it. Remote centralized control is risky for other reasons. Buggy code or a poor ruleset pushed on a friday afternoon would have the same effect. Its bad practice to put all of your eggs in one basket like this. Not everything should be remotely controlled.

Jumping straight to vehicles might be much. But you can definitely start hacking away at small iot devices or routers. They usually have poor/no security and are a great way to get your feet wet.

There are whole youtube channels dedicated to reverse engineering small consumer devices.