The previous owner of my car had a cell wired in, same kinda setup oneothefewproud described. I took the actual phone out, but haven't pulled the antenna yet, as I can't figure out a good way of doing it without 1) screwing up the rear glass and 2) leaving a bit of wire protrouding from my interior ceiling. I haven't figured out how exactly all the wires for it are run either, there is one in the roof, and the one in the center console, I'm not sure where they connect though...

I also left the little ball mount thing on the side of the console on the passenger side, because I though that would look better than having a hole in the carpet and three holes through the side of the console.

The real question is though ... what are the reasons for having a car wired cell instead of just getting a portable these days? Do any cell carriers still sell car-only kits?