TeamPicker is now an Android app for creating teams.
Honestly, this app probably wasn't even necessary as I recently converted https://teampicker.ca to a PWA. This type of app can be installed on Android, iOS, and many desktop browsers. But hey, it was fun!
So basically, this app is what I thought of when I thought of 'web app' back before I knew about PWAs. I guess the only advantage really of doing it this way would that it's not reliant on a user installed browser. PWAs data can get wiped if the user deletes the browser data.
These screenshots are a little old. So don't worry! The app does look a little nicer than that actually!