iphone call audio via dock connector

[Kylegypo]

This is a longshot as I posted this on iPhone jailbreak forums etc but nobody has any answers.
Basically I have an Alpine IDA-X303 with my iPhone connected via the Dock connector.
It lets me control iPhone from the headunit to change track, volume etc but as soon as a call comes in (ringtone plays through headunit/speakers) I answer... voice comes from iPhone speaker... I want to be able to hear phone calls through the dock connector.

Also just a little tip for any iPhone users. You know when you connect it to your headunit and it says "accessory connected" when you go to iPod so you can't view album artwork or change song via iPhone. Jailbreak and download "no accessory splashscreen" from cydia and you will have complete control.