This week France-based Withings began selling its sleep coaching system, Withings Aura, on its website and through Amazon for $299.95. After about one day of sales the Aura sold out, but Withings wrote that it would begin taking orders for the sleep tracker again in a few days. Aura was first revealed at CES in January when the company said it expected to begin selling it come spring.

Aura takes a different form than most other sleep tracking and coaching offerings on the market today since it does not require the user to wear a device while they sleep. Instead, the system consists of a sensor placed in the user’s bed and a bedside device that serves as both lamp and alarm clock, which are controlled by a companion iOS app. The bed sensor monitors body movements, breathing cycles and heart rate, while the bedside device senses ambient environmental factors like noise, light, and temperature. The bedside device also emits light and sound to help users fall asleep or wake up. The program is designed to help relax users as they fall asleep and help them wake up more easily in the morning by facilitating the release of the hormone melatonin into the body. 

“Sleep is such a vital part of a healthy balance that we challenged ourselves to create a product that could be used not only to analyze and monitor sleep, but also to positively impact the experience,” Withings cofounder Cedric Hutchings said in a statement timed with the unveiling at CES this past January. “By combining environmental sensors, light and sound, we’ve been able to create a product that will give users the data and power to improve a third of their lives.”

Sleep tracking and coaching has proven to be one of the more volatile segments in digital health. High profile sleep coaching company Zeo offered up a similar product to Aura before going out of business in early 2013.

More recently a startup named Hello raised millions in a crowdfunding campaign for a bedside, orb-like sleep tracking device called Sense and companion pillow sensor, Sleep Pill. The company subsequently raised $10.5 million to scale the business.

In recent years Jawbone, Basis, Fitbit and others have boosted their wristworn activity trackers with sleep tracking features too.