[Attackers] could alter and forge the readings to cause warning lights on the dashboard to turn on, or even crash the ECU completely.
Wirelessly crashing the engine control computers of passing cars? It's like a sci-fi nightmare come true. Can we please start requiring some sort of "I know what the hell I'm doing" license to be allowed to program things that can kill people? I don't even want to think about the possibility of a buffer overflow exploit.