When I turn on the XGPS160, I get a message on the iPod/iPad/iPhone that says “This accessory is not supported by iPod/iPad/iPhone.” 

Turn the GPS Receiver off, wait about 30 seconds for the iPod/iPad/iPhone to recognize the device is disconnected, and then turn the XGPS160 back on. If the message repeats, turn the iPod/iPhone/iPad off and back on.