Nightkeeper is a calm bedtime coach that helps users stop scrolling on time with one clear nightly rule. Set a phone-down time, choose an early nudge, use a short snooze, and write one personal line that appears when bedtime starts. The app includes a top pop-up test, Coach and Settings tabs, and a simple on/off bedtime rule. Nightkeeper uses notifications, exact alarms, boot-completed recovery, and vibration to deliver bedtime nudges, restore scheduled reminders after restart, and alert users at the chosen time. No account login or internet permission was observed in the reviewed build.