This app shows Pokémons IV perfection(%) for Pokémon GO app, using iOS devices camera.
So you need one more iOS device to install this app besides your iOS device with Pokémon GO app.
This app keeps the image and the values with tapping the screen. You can see them in Viewer page.
This app is made by a fan of Pokémon GO, and it is unofficial.
iOS 15.6 or later