I live in interlaken where a lot of pilots fly cross country. to my knowledge tehy all fly with vario and a power bank during their 100+ flights on their cockpit so i wouldnt worry. else call a tandem company to get more direct feedback from experts

This item is reportedly compatible with all smartphones equipped with IQ.

Iphone yes (if it supports wireless charging), Appel Watch unfortunately not (wireless charging). It works via cable, of course. I hope I could help you further