I can't help myself here.
StarTacs offered by Sprint and GTE (and probably Verizon/Bell Atlantic, but not sure) have the Phone.com microbrowser in them. This means you can screen your email, check your stocks, buy cooks and CD's, find out which movies are playing, find the nearest Kinko's, etc. - AND make calls.
I have no idea whether models these work in the car, but I don't see why not.
The company I work for (Phone.com) pretty much single-handledly invented this technology about 5 years ago, and remains at the center of an industry that has now standardized the approach (see
http://www.wapforum.org). There are nearly 10M people in Japan already using this; there will be millions in the U.S within 2 months. Nearly every phone Sprint sells, every phone Nextel sells - are "wireless internet ready". GTE, BAM, Airtouch also offer the service in the U.S. AT&T and others are following suit within the next few months.
End of commercial.
If you're interested, visit
http://www.phone.com
Yes, it was Phone.com's success that allowed me to buy my M5!