I’ve been using the iPhone’s bedtime feature within the built-in clock app for a couple months now. It used to have a couple glitches, but has started working better for me with time. The feature allows you to set a reminder for bedtime, which I have set to 15 minutes before I’d ideally like to go to bed. Your phone only reminds you if you have been recently been using your phone (it doesn’t want a notification to pop up if you’ve already gone to bed). My favorite feature is the alarms sounds. They are much calmer than your typical alarms, and start off low, with loudness building so that waking up is less sudden.
The one drawback I have is definitely more of a me problem—I am not typically done with work or ready for bed when the reminder goes off, which sometimes makes me feel guilty about not getting enough sleep. Otherwise, the usability is great, and sets you up for healthy habits if you follow your phone’s orders to go to bed. Even if you don’t go to bed when you set the time for, the phone lets you track your sleep hours, which it bases off when you stop using your phone around bedtime and when your alarm goes off/you start using your phone in the morning.