At some time ago, I was looking for a level / clinometer app for iOS that could present the result with six digits of precision, with four decimal places (e.g. 12.3456). I could not find any, so I decided to build one myself.
It was already some three years ago I did my last iOS dev work with Obj-C. Angle Level would be my first complete app to be released at the App Store using Swift. SwiftUI was on its infancy still and some basic UI features was missing, so I went with the goold old UIKit. I build the UI completely in Swift code and aimed to look like a native app. To test how viable App Store is for this kinds of apps, I also monetized the app with basic IAP. Full precision with four decimal places can be unlocked using the IAP.
The final angle measurement is computed using temporal filtering. The app gathers result from 100+ accelometer samples and ditches the samples that deviate with predefined amount from the gathered samples. The measurement is complete after predefined minimum deviation threshold is achieved.
More detailed info of about the Angle Level app can be found at App Store.