I have a UK spec hemi and had a similar sounding chime that was driving me nuts. The radio was on the radio station screen and when the car was started, the satnav was not reading the navigation disc. Because it was not displaying the satnav screen, it does not show the satnaverror on the screen and gives a double ping/chime. Took me a while to figure it out.
If your friend flselects the satnav screen and starts his car, he should see the worded satnav error displayed on the screen - assuming that he has the same problem!
I experienced this not long after buying my Jeep and was worried sick by it expecting the worst form of impending doom. Kept trying to reassure myself that Hey its a Jeep, what could possibly go wrong? (Cue nervous laughter)
Seriously though, hope this helps.
Regards and happy trails for the festive period.