I've used Sleep for Android to track my sleeping patterns since about 2013. I consistently get 3-4 hours of deep sleep per night in 6 hours of actual sleep.

Sometimes it's simpler to watch an hour of YouTube (or post on HN, upvotes are easier at night), than to get up and lay back down several times.

The app pauses sleep tracking when it can tell you're awake. This makes it annoying to see I've been sleeping from 9pm until 7am, and only got 6.5 hours of sleep.