It doesn’t pay much, but if you’re a healthy person and want to make a bit of extra money online, the AchieveMint app will reward you for doing things like walking, tracking your food, or taking health surveys. AchieveMint works by connecting to fitness apps you might already be using like Fitbit, RunKeeper, Healthkit, and MyFitnessPal and then giving you points for certain actions. For every 10,000 points, you earn $10 with no limit on your earnings.
If you have a good idea for an app, and the skills to create it, then producing your own premium app can be profitable. However, with so many free apps available, it may be hard to convince people to pay. If you want to go down the premium app route, consider having a basic free version to encourage people to download the app in the first place. You can then provide the option of upgrading to a premium plan once users realize how useful the app is.