When you need to go somewhere on time (wedding, theater etc.), and you don’t want to nag the kids again and again.
Install the app on your and the kids’ phones. When you need to get going, maybe an hour before, you set up the nagging alert on your own phone. The app will start nagging the kids: “you’ll need to leave for the theater in an hour”, then “… in half an hour”, “… 15 minutes ” etc. The app will use visuals and sound (regardless of the sound settings on the kids’ phone.)