A while ago I made an app for tracking baby activities because I became a parent and was horrified at how many permissions the existing apps required and how much tracking they contained. Both the app and the server are open source.
This is a web-app which also has an Android version in the Play Store (F-Droid didn't accept it because they don't feel like web-apps should be welcome in their store). On iPhones it can be installed as a PWA to the home screen.
Features:
No tracking whatsoever
End-to-end encrypted, no personal information is stored on the server unencrypted
Track baby's feeding, diaper changes, breast pumping and sleeping (more to come)
I didn't find any link to the Git repository from the PWA app.
Also, IMO the best way to make it this kind of application trustable would be to have no backend. If there is no backend, there is no stored data at all.
So as a user, I might prefer to be a frontend only solution which store everything in localStorage and then maybe use a remote storage
the best way to make it this kind of application trustable would be to have no backend
That doesn't work for my family, the data are shared across two people (potentially more in the future), so there needs to be a backend. This also allows for alternative frontends. And as they say, "make the apps you would want to use."
maybe use a remote storage
Remote storage indeed sounds like an interesting technology, but I'm not keen on rewriting the app at this point. Furthermore I'm using the JSON:API standard which I'm very familiar with which speeds up my development significantly.