Ended up ordering the Blitzsafe from logjamelectronics.com
http://www.logjamelectronics.com/blitzhonauxdmxv1.html

Apparently the PIE adapter needs to have a ground attached if you're running a device (like an iPod) on battery only. If you run a device that draws power from the car it doesn't need grounding. You can wire a three position switch if you want to use both -- iPod and Delphi XM.

Instead I got the Blitzsafe which doesn't have that limitation.