Withings Sleep Tracking Pad - Under Mattress SensorThe Withings Sleep Tracking Pad is an ultra thin mat that slips under your mattress to monitor your sleep patterns without the need for any wearable device. Measuring just 0. 2 inches thick and featuring a premium fabric cover, this sleep sensor is positioned under the mattress at chest level for optimal tracking. Once set up with the free Health Mate app via Wi Fi, it automatically detects when you get into and out of bed, tracking your sleep every