I got this response back from a technical help line asking about the GMPD2:
"the GMPD2 will work just fine. It’s a 12 volt charging unit. It can charge newer I-pods with this. http://www.amazon.com/Scosche-passPORT-Charging-Adapter-iPhone/dp/B001HN6CVA
You will have to install this at the XM tuner located in the trunk at the driver wheel well. If you have any further questions let me know. Have a great day."
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I've ordered the interface and the 12v to 5v converter. Should be here Wednesday or Thursday. I'll let you know.