To quote Colin Lawler: “Starting with the last question – smartphones have improved both in terms of processing capability and speaker and microphone quality. When combining this with a revolutionary.and patented, new approach to sonar, we found a way to enable a pretty clear picture of the respiratory pattern and gross body motion which enabled us to leverage our years of work developing algorithms for the hardware platform. This was a breakthrough, originally developed and patented at the University of Washington, then substantially added to by the expertise of ResMed Sensor Technologies in Dublin. All of this made it possible for the first time to convert most smartphones into a highly reliable physiological sensor from which we can derive an accurate SleepScore.”
https://www.medgadget.com/2018/10/sleepscore-labs-non-contact-no-hardware-sleep-monitoring-system-product-review-and-interview-with-ceo.html