voice recognition
The M class does not have steering wheel controls for the audio but you can get a Voice recognition unit (a lever with a mic) that gets mounted on the steering wheel column, right across from the cruise control lever. It sells for about $480 US. I've heard that the installation is straight forward. You basically pull the lever, and say "radio on" to turn on the radio - or something similar.
I haven't isntalled it yet - still researching b/c the MBUSA website states that you have to have the phone installed to make this work. Others have done it w/o the phone.