The bluetooth in the 07 and 08 w211, probably others, is only for phone calls. It does not support any other Bluetooth options, such as music playing. I've been able to get it to work fine with my iPhone 8. It was not specifically designed for iPhone, although it probably didn't test against Android, since Android only launched in 2008.

As for other dongles, it can have either an AUX plug or an iPod (32-pin) plug attached, coming into the glove compartment. These allow music playing, and even controlling the iPod/iPhone play from the steering wheel. The volume, however, tends to be very low power. There is a box under the passenger footwell where the iPod plug connects. Not sure whether the AUX plug goes through the same box, or just directly to the small plug on the back of the COMMAND module, I only had the iPod connector on my w211 when I got it.

Am currently struggling with installing one of the Seicane stereos. Maybe I'll figure out more about all this once that is done.

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1976 240D [W115.117/616.916] (acq 11Jun76)
1990 MB 300D 2.5 Turbo [W124.128/602.962] (acq 4Sep15)
1991 SL250D (ex-300SL-24) [R129.061/OM602.962/722.6, was M104.981] (acq 25May12, converted to diesel)
1993 Jeep Cherokee [XJ] (acq 12Apr14)
2008 E320 CDI [W211.022/642.920] (acq 27Jan24)

-- Deceased...
1993 300D 2.5 Turbo [W124.128/602.962] (totaled by Dominos driver 28Mar12)
2007 E320 CDI [W211.022/642.920] (totaled 18Dec23)