Audio out through dock cable?

[Avid]

Anyone know if there is a custom cable out there that will give audio out through the iPhone's dock cable?

Basically...

Dock at one end ---> 1/8" stereo plug/usb connection at the other

I'm lazy and don't want to plug in more than one cable I was looking at the ProClip holder and wanted something to permanently install in the truck and get rid of extra cables.

[innerealm]

Just run a double head phone jack one cable or if you want to carve at the same time I've seen one by geffin that charges and has a short cable from the holster that plugs in

[Avid]

I only want to plug it into the dock, I don't want to have to plug in the audio input too.

But I'll check Griffin

Thanks

Griffin Tech Support said this one should work

Review: Griffin RoadTrip with SmartScan (2008) | iLounge

It has a line-out on the base