Im the second owner but it doesn’t appear to be used at all. We bought it for our expected child but due to bad luck among other unfortunate things that have happened it the past couple months I’m selling this. The Smart Sock 2 uses pulse oximetry to track 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 if your baby's heart rate or oxygen levels fall outside of preset zones. I’m asking $125 pp g&s.