The one I gave will support navigation through iphone. A word of caution here. Having all the controls on one system may create issues. The rear camera ,when in action you will not have control over the music system. So, if you add Navigation to that , it will increase the dependence. There are systems available with Navigation interface.Like this
Read through for more info in the pages.
Optional Bluetooth Adaptor KCA-BT300
The KCA-BT300 is an add on Bluetooth adaptor compatible with the DPX504U. It enables hands-free mobile phone operation, SMS (Short Message Service), additionally it plays music files from A2DP-compatible devices.