A foreign currency converter for travelers
The Flutter app was created originally for State Management With Provider at Kodeco, which at the time was raywenderlich.com (so the open-source license is still the one they used). See the tutorial branch for the original code. Later, I got permission to use the app for the article Flutter programming on your phone. And now I'm continuing development because it's a useful app and I'll see if I can make a few dollars selling it.