I’d imagine it’s the same as personal finance apps. A spreadsheet can be enough, and it is enough for a lot of people, but a custom app can make things easier:

• reducing the friction of keeping track
• built in visualizations
• alerts
• integrating the data with other tools

etc.

Something being FOSS doesn’t necessarily mean it’s safe / ethical, but a LOT of FOSS apps are designed with those principles in mind.

However, being FOSS means that if an app claims that it is safe / ethical (ex. In this case, not storing data anywhere but on your device), you or an experienced peer can check the code to verify that fact.

Good note, I didn’t notice that in the original post. I edited the title

I wonder if there is any pattern to those numbers

edit: ah I didn’t notice, thanks all :)