Owlet Smart Sock 2 Baby Monitor Everything included and works Peace of Mind with Smart Sock 2 Peace of mind in parenting is closer than you think. The Smart Sock 2 uses pulse oximetry to measure your infant's heart rate and oxygen levels while they sleep. This information is communicated to your phone via a base station that is designed to notify you with lights and sounds if something doesn't appear to be just right with your baby. Using our app, you can view your baby's heart rate and oxygen levels in real- time.