Grows With Your Child: Includes left and right fabric socks for babies between 0 - 18 months (up to 30 lbs). Integrates with Owlet Cam (sold separately). Owlet’s free baby monitor phone app gives you real-time notifications and let's you see your baby’s heart rate and oxygen levels from anywhere. Available for iOS & Android. 16 Hour battery life - 8 hours in 20 min., and a full charge in 90 min. Safe. Secure. Proven: The Smart Sock baby monitor uses established pulse-oximetry technology proven safe for babies and children, and the secure and encrypted data means only those you choose can access readings from the Sock. Worry Less and Sleep Better: be notified from anywhere when your baby needs you by lights and sound through the base station and phone app notifications. Track Heart Rate, Blood Oxygen Levels and Sleep: The award-winning Smart Sock is the first ever baby heartbeat and breathing monitor to track your baby's well-being while they sleep.