There are a lot of watches and rings (applewatch, ouraring, garmin, ...) measuring sleep quality, but they do this mainly through models trained on blood glucose and motion.

The main way to measure sleep quality is using an EEG. There are 3 options.

I've opted for the cheapest tier to start and will explore the later ones after.

More notes:

Now lets discuss the data pipeline. See this vid

The graph we're mainly interested in is the hypnogram; it is a graph that represents the stages of sleep as a function of time.

Lastly there's other apps worth trying like Dreamento or EEGLab.