You don't need to bother with the BMW apps just download the Tunein Radio app - just checked mine and Planet rock is on there.
Haven't played in a Bm yet but in my Audi I just plug it in and off it goes. I'm guessing you have enhanced BT so that should make it easier just to launch the App and I would have thought you can control from there.
Even if you can't it won't be any worse than controlling the DAB through an additional unit.
Give it a go, would be interested in your feedback as I don't have my new car till Monday!