To show my children (which are not that interested to see that :-) the architecture of Android apps (lifecycle, listener) and to show how easy a basic app can be written I build this simple compass app.
It is available in the Playstore and may be used by everybody, but it is not meant for widespread use. It expects a recent device. But it works (offline! :-), is free of ads and in spite of the fact, that it is in the category of compass and weather apps, it doesn't need access to your contacts :-)
You can see the source code by cloning or forking the git repository https://github.com/rbudde/c0mpass.git .
You may create issues on github if you detect errors, want some new features, etc. Pull requests are welcome. But note, this is not a product developed in an agile environment :-).
For suggestions, discussions, questions contact me at reinhard.w.budde at gmail.com