Since extensions has been abandoned I'd considered two things.
1. Buy an android phone and use AppRadio Unchained, I actually did this and bought a HTC One M8 but I didn't like the Android system as a phone and decided to sell it and bought a iPhone 5S.
2. Upgrade my AppRadio 2 to an AppRadio 4, but with mixed reports on the unit/carplay, and the cost envolved.
I decided to try something else before I abandoned my AR2.
I bought a cheap Quad core android HDMI stick for €35 from Amazon. Installed the free version of AppRadio Unchained and paired it with the radio. It gets it's internet through personal hot spot on my iPhone.
I also paired my iPhone 5s with the radio as a special device so I can still make/receive calls through it.
I'll post a video later but it's great, I have all my apps installed on the hdmi stick, spotify, YouTube, Waze, Google maps, etc and I still have the ability to use my iPhone. Its actually easier than using the iPhone with the radio as all I have to do when I get in the car is turn on personal hot spot, I can then leave my phone in my pocket.