Good question!

I know that when I had a computer in my car (full xp system that went to a 7" Touchscreen up front) I was able to use my xp system as an audio gateway via bluetooth. Set up a macro to hook up with a touch of a button and off i went. If the bluetooth profile is there I see no reason why the same thing could not be done. You wont be able to access your contacts and such from teh n810, but i never really felt the need to. Mos the peopel i talk to are set up as speed contacts. Sit down, press a button on the n810 to connect as a audio gateway plus mic and then speed dial off the phone (Hold down the number 3 or whatever) I suppose you could even use voice commands with the mic.

In conclusion:

All i really need is to use the n810 as an audio gateway and mic like you can on the windows XP bluetooth Stack.

I haven't tried it, it might even work ... but consdering A2DP isn't 100% there either, I'm not terribly optomistic. I'll try here in a few mintues and see what i come up with.