This app was mentioned in 3 comments, with an average of 2.00 upvotes
I looked in to this on my Honda CR-Z which I'm guessing has the same horrible antiquated Nav/Audio system (hasn't had a real refresh since 2004). There is PodMode if you don't mind building a custom cable to hook up your phone. Check it out here: https://play.google.com/store/apps/details?id=me.spadival.podmode&hl=en
Having a look there's this https://play.google.com/store/apps/details?id=me.spadival.podmode which might work, but it seems you may have to make a custom cable. Does your stereo have no aux input?
Apparently that's possible if you make a custom cable.
https://play.google.com/store/apps/details?id=me.spadival.podmode