This app was mentioned in 2 comments, with an average of 2.50 upvotes
I created a fitness tracker app. It's on the market since the beginning of this month and so far I've made 9$ with banner ads. I didn't do any paid advertising or much marketing, so the 5 downloads I get a day are through SEO. I mostly did it because I use the app myself and wanted to try React Native. If your only motivation is making money, I think in 99% of the cases you would be better off as a developer creating someone else's apps for a salary.
Created a workout log for the PHUL program. I think one of the reasons why people like Stronglifts so much is because of the app, and many are transitioning to PHUL afterwards, so I released a similar app for the PHUL workout. I hope it helps some people who were looking for the same.