We have EU holidays booked until January next year and usually pay as we go on Zero Santander credit card which gives good rates without charges.
We were concerned about negative currency rates following the Brexit vote. A low rate wouldn’t support our pay as we go past strategy.
The app is excellent and we are topping up every time we see a good rate (like today at 1.196).
This has allowed us to hedge our holiday spending just like the big companies.
One suggestion: Could the app alert you once a desired exchange rate is reached? You could then decide whether to top up or not.