There are two basic types: audio and video/audio. Some are analog, others are digital. All monitors operate within a selected radio frequency band to send sound from a baby's room to a receiver in another room. Each monitor consists of a transmitter (the child/nursery unit) and one or more receivers. Prices range from about $25 to $150 for audio monitors and about $80 to $300 for audio/video monitors.
Baby monitors are just one way to keep track of your little one. For newborns, the Snoo Smart Sleeper is a bed that gently rocks your baby for better sleep, and connects to an app on your phone that lets you receive alerts when your little one needs attention. The Owlet Smart Sock 2, meanwhile, is a connected pulse oximeter that allows you to check on your baby's vitals any time through an app, and will notify you automatically if there's a problem. The Sproutling from Fisher Price is a motion and heart rate sensor that straps to the back of your baby's calf and collects data while he or she sleeps.
Gone are the days of silently peeking into the nursery to check on your napping baby and then, whoops, accidentally waking them up (“No, no, please no!”). A baby monitor uses a camera to watch over the crib, while you carry a handheld device that lets you know what’s going on with your child at any given moment, no matter where you are in your home. There are also other monitors that track sleep or breathing either with a clip or sock.