To chime in (I'm not the original commenter you're replying to), in theory someone could develop an Internet-connected gadget, break into your car without being detected, plug said gadget in, and then drive you into a wall or off a cliff, maybe that's what the grandfather poster is worried about.

But in reality, no one's develop that sort of tech, and if a baddie wants to kidnap or kill, they'd probably spend their resources somewhere rather than hacking such a tool.