Fit for Growing Babies: The Owlet Smart Sock Baby Monitor fits most infants from 0-18 months or 6-25 pounds, perfect for your growing bundle of joy. Real-time view: 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. Compatible with iOS (iphone) & Android. Proven: uses established pulse-oximetry technology that has been proven both safe and accurate. 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.