Safety for your baby. The Owlet Smart Sock is the first baby monitor that tracks your baby's oxygen levels and heart rate while they sleep. Parents around the world trust Owlet every night. The award-winning Smart Sock goes beyond the capabilities of any other baby monitor. Oxygen levels and heart rate are the best indicators of your baby's health. If your baby's readings leave the preset safe zone, you will receive a notification on your mobile device and at the base station.