This app was mentioned in 9 comments, with an average of 1.56 upvotes
That would be GoCalc. Another in-app IV calculator I like is PokeGoMaster. GoCalc probably has a slightly better interface, but PokeGoMaster shows a bit more detail.
Fwiw, I prefer Go Calc to CalcyIV. It's also an overlay, but instead of the permanent bubble, it's just a low priority notification in the notification shade.
Also screen reads.
Go Calc for Android has been fixed, if you're looking for an Android alternative.
I like this one: https://play.google.com/store/apps/details?id=scave.gotools
Go Calc for Android has been updated and works for the new CP calculations!
Go Calc for Android has been updated fully! It scans your Pokémon automatically and saves a list of your calculated IVs: https://play.google.com/store/apps/details?id=scave.gotools
Go calc for android has been updated.