Another option is the Dice mediabridge now sold by Audiovox. The following is an Amazon price:
Amazon.com : DICE MBR-1500-BMW MediaBridge with Bluetooth for BMW - Black : Vehicle Audio Car Mounts : Electronics I think it is the best thing short of changing out the Nav screen. The only negative is this option disables the CD player and you have to run wires from the rear to where the media bridge is installed near the radio. The instructions are very helpful with pictures and tech support is available. The following is a youtube video of the install:
BMW X5 - Pt 2/4: Soundplicity iPod / iPhone / Android Kit Installation Instructions - YouTube
The following is a link explaining features:
DICE Electronics LLC - DRIVE | LIVE | ACCESSORIZE - MediaBridge
They offer a DSP and non-DSP version. I purchased the Sirius radio option rather than using an app. Everything is controlled by existing radio buttons.