Hi...was looking for an "invisible and handy" solution, and i found your post.
I've just order this: http://www.bee-wi.com/bluetooth-car-...,BBA100-A0.cfm
It might be the solution you are looking for. You just need an usb charger to plug in the power. It should be enaugh invisible as i will forget it under the armrest (i just hate to see aftermarket things into my car!).
I'll write a review as soon as i receive it.