As someone who has done pretty extensive research into CarPC's I can say that the "state of the art" today doesn't really come close to what it truly needs to be to operate in a car. Full-fledged, or even half-fledged (intel NUC) PC's just aren't designed for a car environment. There's the vibration, the user interface, the power requirements, radio interface, speaker/amp connections, etc... Sure, there are some mitigations such as using an SSD, using something like Unity or a netbook or tablet interface, and some power conditioners, but that is all a kludge that your average consumer won't even consider.
Through all the research I did to try to find some solution to my older BMW's stock 1 cd changer and digital watch display, I came across these, which are drop-in replacements for your stereo and many come in two flavors. They all have a base embedded OS that offers bluetooth for hands-free calling, basic radio functions, media playback and even iPod interface. They also come with a second physical board within them purely for navigation, one runs Windows CE, the other runs Android. I can honestly say that the Android deck is pretty damned useful for navigation. I just downloaded CoPilot and all the maps I needed using the built-in wifi as I sat in my garage and I get a navigation solution much like a Garmin. Is it perfect? No, occasionally it will crash reading some music from the SD card input it has, the touch screen is a little inaccurate, and I can't completely customize the look and feel. However, it does what it needs to do 98% of the time.
Googles Android is defective by design since they only publicly release the bare-bones, no frills or shiny features code. A car doesn't really need all the fance Google App integration, I know if I'm driving I don't want gmail or google+ harassing me. Any car manufacturer could take that free source code and make a useful OS out of it... they would just rather shoehorn something somebody else made into something it wasn't designed to do, all in the name of saving money.