Just heard of this supercool accessory today. Its not only a bluetooth speakerphone for your car, its also an FM transmitter that streams your music through your car stereo! AND when you get a call, you have the option of using the built in speaker, or using your car speakers! It also supports voice activated dialing, caller ID and verbal notifications.
I think its pretty sweet. I've checked out a few reviews and everyone seems to like it. It sells for $119.99 CDN which isn't bad for what you get. It claims to run for 13hrs of talktime before needing a charge.
It also works with GPS mapping applications. I'm not exactly sure which ones though. More info on GPS functionality for BB here: http://jsbbblog.blogspot.com/2009/04/got-gps.html.
I better start saving. This seems to be the solution for those of us that have cars without bluetooth built-in.