I have the 'Stock radio' - and was looking for something to get to enhance using NAV off of my Cell Phone. I found this on Amazon and decided to try it:
I installed WAZE NAV app , along with Amazon music on my phone - and using FM feature I was able to feed 'Directions and Music into the stock head unit. VERY NICE! Worked just like a factory NAV system with directions overriding any music that was playing- and 're syncing' directions if a wrong turn was made.

Amazon.com: Avantree Roadtrip - Bluetooth Speaker & Wireless FM Transmitter Kit 2-in-1 for Cars with Hands-Free 6W Speakerphones, Built-in Mic, and Multipoint Cell Phone Connections : Cell Phones & Accessories
Buy Avantree Roadtrip - Bluetooth Speaker & Wireless FM Transmitter Kit 2-in-1 for Cars with Hands-Free 6W Speakerphones, Built-in Mic, and Multipoint Cell Phone Connections: Speakerphones - Amazon.com âś“ FREE DELIVERY possible on eligible purchases
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