Charging status of phone may work.
I always charge my phone at night in the bedroom.
Can maybe use Tasker? To sense when the phone has gone from charging to not.
Although if the phone battery is low before I’ve retired for the evening I may plug it in downstairs, so not 100% a solution., unless in Tasker I could also specify a time range for am when it can only trigger.
I want my curtains to open in the room when I’ve gotten out of bed and maybe automate some other things.
I dont have a set routine so no regular morning wakeup alarm at the same times.
I thought the NFC tags might be a tap type thing but wasn’t sure.
Pressure sensor under the bed probably the best thing but want a cheap no thrills solution.