I'm sure there is if you went through the diagram. But if you're going to be putting in an aftermarket HU, why not get one with iPod controls if you have an iPod?
Pioneer came a long way with their ipod controls now, especially allowing video playback. I know it seems nice to be able to use that oem port, but it's primitive if your using a touch screen of any type.
Pioneer has made leaps and bounds on the interface, it looks like a standard ipod wheel on screen and functions the exact same..