Here's a question that's been bugging me for awhile:

I've been using a standard Apple USB<->Lightning cable to connect my iPhone 6 to my iDriveless-but-BlueTooth-capable E91. This "works" in that it does what I want most, which is to route audio through the built-in stereo so I can hear voice navigation (and even stream internet audio) from my phone. But this doesn't seem to charge the phone at all; the best it seems to do is slow the rate at which the phone discharges by a little bit.

BMW makes this thing which costs a lot more and is going to require an extension cable to reach my phone. What does this do beyond what an ordinary USB<->Lightning cable does?