Spirax, in the twisted paranoid mind of American security consultants, the fact that a passenger might know exactly where the aircraft is, via GPS, is only a very short step from the passenger seizing control of the aircraft and directing it, via his little GPS, somewhere harmful.
To put it another way: "Ignorance is strength!" What possible legal reason would a passenger have for knowing where he is? Trying to acquire such information is therefore obviously suspect.
Regarding CASA, there is a requirement in VFR for the pilot to fix their position every Thirty minutes. I prove I do this by marking my paper chart accordingly. I believe that some, but perhaps not all, CASA staff will also accept a stored iPhone or iPad forecast acquired via NAIPS as evidence of complying with the weather forecast requirement.
However, if your battery runs out and you ain't got pencil and paper chart, you are most probably stuffed, unless you have the time and capability to build a gridded sheet and start plotting lats and longs from ERSA, marking in Navaids, etc.
Clarification from CASA would be nice to have.
And a P.S. If I was flying outside my own patch, I would want a manual backup or Two apart from the iPad anyway. I can testify from my marine experience that when your GPS/Plotter/Compass/Autopilot system goes tits up in the middle of the night or bad weather it is extremely disconcerting until you drag out your paper chart and start plotting.