Thanks for your recommendation. And no, of course, I do not use it in the flight as mentioned. We are also, not allowed to use any software on iPad or phone to navigate, we may only use the equipment in the aircraft. Software like Sky Demon are only allowed for planning.
And when reading the example with the student you had, I completely agree with what you say. I would never fly like that. Even if my battery went flat, I have a mini handbook (physical) with me, that can be in the side pockets, which gets renewed every year and contains all airports in Denmark, frequencies, and most important information, and I also have a VFR map with me.
So a flat battery won't be a problem for me. And in VFR you must have visual contact, so even if all your navigation instruments fail, you should be able to navigate visually with your VFR map.