Bluetooth Speakerphone Software

I love my Powerbook. I love my bluetooth-enabled Nokia 6600 cell phone. I love that I can synchronize my contacts and my calendar between the two of them. It's nice to be able to receive SMS and caller ID in a window on the computer, or at least it would be if I got decent T-Mobile reception in my apartment.

What I don't understand is why I can't use my Macintosh's built-in microphone and speakers to serve as a speakerphone for my mobile phone. I don't know enough about the Bluetooth specifications to know if it's technically feasible with the current generation of the specification. If it is, it's just a little piece of software that somebody should write; if not, it should be added to the next generation of the spec.