What are sleep tracking apps and how do they work?

ok.co.uk:

Sleep tracking apps have become increasingly popular recently and can be accessed via smartphone apps or using wearable technology for the wrist or finger.Though, less is known about the science behind them and how the apps actually work.

Sleep expert and scientist at Emma Sleep, Theresa Schnorbach spoke to OK! about sleep apps and how they work.Theresa explained that the apps function by using “accelerometers or small motion detectors” that measure how much movement you're making while you sleep. “An accelerometer is fairly accurate at interpreting some sleep measures, but not all.

For example, if you lay still in bed for a period of time trying to fall asleep, the accelerometer may interpret that period as sleep. “Some sleeping apps are able to interpret an individual's shape and movement - measuring factors such as breathing rate, and body movement, then turning those insights into a record of your nightly sleep patterns.” It’s no secret that a good night’s sleep sets you up for a good day so tracking apps can provide an insight into sleep habits while also making users mindful of their sleep hygiene practices.Though, Theresa adds that using sleep tracking apps are not always fully accurate. “Feeling rested after a night’s sleep requires waking after a sleep cycle is over and sleep trackers can give a better understanding of how long each sleep cycle lasts to help us make better decisions for our sleep.