aux cable kit for 4.8is with Nav and DSP???
 

Is this what I need from ECStuning?
82110149391 - Auxiliary Input Retrofit Kit - ES#194847

Or do I need something more expensive from Bavsound?
BMW iPhone, Bluetooth, iPod, Android, and Smartphone Integration, plus SiriusXM - SoundPlicity Control | BAVSOUND

I purchased the simple cable with 3.5mm jack to aux fitting from an eBay seller (for input to Nav unit aux plug). Installation was a breeze by removing the climate control unit and reaching up, then routing cable to ashtray (a small hole must be drilled in base of ashtray). It won't charge your iPod/iPhone but plays music no problems. I did notice that when I have my usb charger plugged in to my iPhone and play music at the same time, there's a horrible static noise that comes through the system. No problem though - just ensure your iPhone isn't being charged when you play back music and it's fine.