In the past 2 years, a new class of infant physiologic monitors marketed to parents for use in the home has emerged. Smartphone applications (apps) integrated with sensors built into socks, onesies, buttons, leg bands, and diaper clips have the capability to display infants' respirations, pulse rate, and blood oxygen saturation, and to generate alarms for apnea, tachycardia, bradycardia, and desaturation (Table ). Despite the lack of publicly available evidence supporting the safety, accuracy, effectiveness, or role of these monitors in the care of well infants, sales of these products are brisk and the market is expanding. For example, the makers of a "smart sock" monitor (Owlet Baby Care) that claims to alert parents if their infant stops breathing 1 recently reported sales of 40 000 units at $250 each. 2

Smartphone-integrated consumer baby monitors that measure vital signs are popular among parents but are not regulated by the US Food and Drug Administration (FDA). 1-4 This study measured the accuracy of pulse oximetry-based consumer baby monitors using an FDA-cleared oximeter as a reference. Methods | We purchased the only 2 currently marketed smartphone-integrated consumer baby monitors that use pulse oximetry, the Owlet Smart Sock 2 (consumer monitor A) and Baby Vida (consumer monitor B). We enrolled infants aged 0 to 6 months hospitalized in general pediatrics and cardiology wards at the Children's Hospital of Philadelphia from July through December 2017. Infants were excluded if born before 34 weeks' gestation, critically ill, anemic (hemoglobin <10 g/dL), febrile (≥38.0°C), hypothermic (<36.0°C), hypotensive (systolic blood pressure <60 mm Hg if 0-28 days old or