Start Sleep Tracking based on Ambient light switchoff

Please provide a mode to start sleep tracking when Lights are switched off. May or may not (configurable) prompt (audible) the user to just click a large icon Yes or No to start sleep tracking the moment when lights are switched off.

Daytime naps or sleep may require clicking the moon sign to start tracking.

Many nights I simply am too sleepy to remember starting tracking but and an audible prompt with easy start, at time when mobile detects lights switch off, would just be the thing.