I especially like to create new features for my mood tracking app Moodistory that are useful and that I don't find in any other app.
One of such a feature is the newly added CSV import: It's designed to let you import any CSV file as long as it has a date, time & mood column. It means that it's easy to import existing data from Google Sheets etc. but will also make it easy if you would like to switch to Moodistory from any other app.
If you try it, I'll be more than happy to know what you think about it!