I have used Nokia CARK-112 and CK-1W with my cars (W208, W203, R170).
We had some discussion about the topic in below threads:
http://www.benzworld.org/forums/forums/thread-view.asp?tid=1192156&posts=10&hl=bluetooth
http://www.benzworld.org/forums/forums/thread-view.asp?tid=1183799&posts=4&hl=bluetooth
We had some discussion about the topic in below threads:
http://www.benzworld.org/forums/forums/thread-view.asp?tid=1192156&posts=10&hl=bluetooth
http://www.benzworld.org/forums/forums/thread-view.asp?tid=1183799&posts=4&hl=bluetooth