I use "Sleep as Android".
- Sleep tracking in an attempt to wake me up 30 minutes before my alarm depending on my sleep cycle.
- Smart watch with the same app for increasing the accuracy of sleep tracking by giving access to my pulse.
- NFC Tag. Using one of the settings from the same app. I've connected it to an NFC tag in my living room. I can't turn off my alarm unless I scan the NFC tag. Nor can I turn off my phone, snooze the alarm, or lower the volume.
You can usually tell by their feet. For example, if they're behind their head.