There is actually a pretty popular open source ECU called MegaSquirt, and yeah, it doesn't need a full multi-user OS. It's mostly popular with racing types. In any case, I'm not really sure I follow what you're upset about, though. You talk about "running MeeGo" on a hardware peripheral device without a processor; I don't understand who you think is saying that.
Besides, if the central IVI box that is connected by CAN bus or whatever to the ECU, the sensors, the security system, etc. *is* running MeeGo, when those other systems are essentially microcontrollers, how is "the computer" *not* "running MeeGo"? Do you say that your desktop box "isn't running Linux" because there's someone else's code running in the BIOS, the hard disk firmware, DVD drive, and Ethernet ROM?