Google wants to be the center of the information universe, so how long do you think it will be before they make a car stereo (which is much more than a standard car stereo of course)?
It can be done now if you want to hack it together, but it would be nice if it was an “all in one” setup. For example, you could take this car stereo (which is really a full blown computer). Add a USB Bluetooth adapter to it and you could use your cell phone as an Internet gateway wirelessly (you can still make/receive calls while using it as an Internet gateway). Higher speed cell phone Internet access in the coming months is only going to make this more attractive.
This would pretty much make all existing navigation systems outdated because map and navigation data would be fed in realtime (based on Google Maps/Earth), and it would be trivial for Google to add live traffic data to Google Maps (not sure why they haven’t already done it). That could also put the XM NavTraffic service out of business (at least heavily cut into it).
Google’s already doing a “mini” navigation system for people with GPS enabled cell phones with their Google Mobile application.
Besides all that stuff, you could stream Internet radio stations, pull up music via iTunes, access your iPod, or anything else a normal computer with Internet access could do.
If someone at Google reads this, and decides to make it their “20% free time project” (this would be my project if I worked at Google), I want one when you are done! heh