How did the application Sleep Cycle initially measure sleep patterns non-wearably?

Using the smartphone’s microphone and accelerometer on the mattress.

The application Sleep Cycle represented an early form of non-wearable, ambient monitoring that gained traction during the smartphone boom. This method utilized the existing sensors within the mobile phone itself, which was placed on the mattress near the user. The system interpreted sleep patterns by analyzing two key inputs derived from its position: vibrations picked up by the accelerometer, indicating movement, and sound detected by the microphone, which could potentially identify disturbances or breathing patterns. This reliance on interpreting vibrations caused by movement distinguished it from the later, body-worn devices.