There are at least five YouTube videos of ATC communications with pilots in trouble because of an IPad failure.
You're talking about what's known as an electronic flight bag, which is using a tablet as a replacement for paper maps and charts. This is legal and has been for some time.
What I and Animats are talking about is running an app on a ipad as a "replacement" for equipment or training that is required for safe, legal, operation. NOT legal.
Here's the cockpit of the Gripen, Saab's current fighter aircraft.[1] One big screen across the whole panel. No sign of a classic altimeter or compass. There's a HUD as well, so there's a second device for the basic flight instruments.
[1] https://bestfighter4canada.blogspot.com/p/the-saab-gripen-do...
Very few pilots manage to earn a lifetime ban.
It's really quite brilliant.
The way that you get pilots to do it is that if you drop the dime on yourself it actually gives you virtual immunity from consequences, as long as no injuries or serious damage actually occurred. The idea is to actually find systemic process/procedure issues.