I too am looking for a bluetooth solution for my '00 E430, but there aren't a lot of solutions out there for Mercedes in general.
This is what I found in the way of installed bluetooth kits:
http://www.behandsfree.com/category.aspx?categoryID=1
I would think any of these could be installed nicely, but it looks like the Parrot models would work the best and you could have the unit mounted in the sunglass holder under the radio. Hopefully this helps.
