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.
The features we focused on were those we thought either increased the performance of the monitor or made it more user-friendly for parents and increased the odds of getting good quality sleep. We looked for monitors that have sound activation that keeps the parent unit quiet when the baby isn't crying, so parents can potentially fall asleep faster because they don't have to listen to white noise. Some of the monitors were so loud, even at low volumes, that the white noise might keep light sleeping parents awake; this defeats the purpose of having a video product to begin with. We also liked the models with screens that automatically "wake" and/or go to sleep.
As you’d expect, the talk back functionality and audio quality in general are great—easily better than the crude talk back features on our video monitor picks. With the battery lasting about 19 hours on a full charge, this monitor had the strongest battery life of any in our test (not entirely a fair comparison, as this is the only one with no screen to power). Rated to a range of 1,000 feet, it exceeds the range of our pick (700 feet) both as advertised and in practice during tests.
The new voluntary ASTM International F2951 standard has been developed to address incidents associated with strangulations that can result from infant entanglement in the cords of baby monitors. This standard for baby monitors includes requirements for audio, video, and motion sensor monitors. It provides requirements for labeling, instructional material and packaging and is intended to minimize injuries to children resulting from normal use and reasonably foreseeable misuse or abuse of baby monitors.
Video, Audio, or Both: First-time parents are suckers for high-definition, night-vision baby monitors where they can pick up on exactly how their child’s chest is rising and falling. You will do this dozens of times a night. Past the Sudden Infant Death Syndrome-scare age, you may just want an audio baby monitor (which a lot of video ones double as), because you’ll know an “I’m hungry” cry from an “I lost my sock” whine.
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.