Owlet's smart sock is made of a soft, hypoallergenic material, providing optimum comfort for your baby's foot. It has an adjustable strap to make sure you get the perfect fit. Their base station does all the heavy lifting. It acts as a charging dock for the smart sock and uses Bluetooth technology to connect to the smart sock. It also connects via wifi to your smartphone or computer to relay real-time information from the smart sock. While the iOS app isn't required to use the Owlet Smart Sock, it provides an extra level of information for parents by displaying your baby's current oxygen levels and other important facts. The Owlet Smart Sock is available for pre-order for $250.00.