So here’s how motion detection works within Sleep Cycle.
With the microphone - This is our recommended option. It’s way more powerful than the others. And anyway, the microphone tracks your sleep using the sounds we pick up from you, during the night. We use these sounds to analyse your sleep quality, and among other things we filter out how much you move, the noises you make, if you snore or cough, if you’re in deep or light sleep, and so on. Our ability to inform on and help you with your sleep is substantially better with the microphone option.
With the accelerometer - If you go for this one, we use the phone’s inbound accelerometer to detect your movement patterns when you sleep, helping us figure out if you’re in deep or light sleep. We don’t record sounds. And this option requires you to have the phone in your bed.
With the Apple Watch - Using the watch is like going for the accelerometer option, but on the Watch instead. We don’t record sounds from the Watch. User who enjoy their tracking to be completely autonomous, tend to prefer this option before the others.