How about compatibility with aftermarket head units?

 

the voice thing wont work, otherwise yes it can be



*edit* yes it can be done, I used to know how but have since forgotten...there are no how to threads to my knowledge. About a year ago I looked and looked for a how too. The best I got was "my installer did it..."

I assume it works with some sort of relay or a seperate speaker all together.

 

HU compatibility, yes. Retrofit the factory nav. into a non nav. car is possible but labor and cost prohibitive. It would be far cheaper to go aftermarket and take advantage of the higher quality aftermarket at a lower cost.