I have, many times, accidently hit the End Turn button when I actually want to use an item. This unintentional mistake can cause me to lose a fight, or when I am close to completing a quest trial, and it is frustrating. Not that it's a big deal but it is something to consider on.
The End Turn button should be displaying a message if there are still characters whose turn is still on. Like, "Are you sure?" "'yes' or 'no'". In fact a lot of stuff in this needs this feature. I often hit the Town button right after finishing a fight, and at the same time a bundle comes up, and I hit a bundle to be purchased. If buying on the Ipad didn't require password comfirmation, I would have bought a lot of those accidently.
Another way to implement the button is maybe change the appearance of it a bit, say make it a BIG RED BUTTON, or place it somewhere else that is not in the middle of all those buttons. If I can hit the wrong alphabet on the ipad keyboard, then I can definitely hit the End Turn button which is right next to the Item button.
My two cents but I think this would improve the game at least on interface design.