A dension gateway 500 with a2dp adapter or Mobridge unit.
I think the BMW combox may have some option for this but if you have an older car (meaning older than 2011) the things you have to do are pretty extensive and expensive for a factory solution if its even possible.
There are some cheap adapters that go through the aux but the aux
is generally regarded as a low fi input.
I'm not clear if anybody makes something that goes in through the USB input that's any good, but it seem like it would be a better way to go.
This is the combo box thread
but its only for idrive I think.