Reading/relaxation timer before sleep

I like to read before going to bed, and I usually set up my alarm and start the sleep tracking before I start reading so I don’t have to check my phone afterwards and I can go directly to sleep.

However, it’s hard to keep track of time and I often find myself reading much longer than I planned.

A feature to set up a timer that notify you with a gentle sound or a vibration when it’s time to go to bed would be nice. The timer could be turned off with the push of a button , so you wouldn’t have to look at the screen, and once it’s off, the sleep recording could start.

For example:
11pm - set up alarm, go to bed, put phone on nightstand and start reading
11:30 pm - phone vibrates, time to turn of the light and sleep recording starts