Wiktionary
n. 1 An intercom system that enables a person to remotely detect sounds of distress from a baby; a baby alarm. 2 A device used to measure the vital signs of a baby.
Wikipedia
A baby monitor, also known as a baby alarm, is a radio system used to remotely listen to sounds made by an infant. An audio monitor consists of a transmitter unit, equipped with a microphone, placed near to the child. It transmits the sounds by radio waves to a receiver unit with a speaker carried by, or near to, the person caring for the infant. Some baby monitors provide two-way communication which allows the parent to speak back to the baby (parent talk-back). Some allow music to be played to the child. A monitor with a video camera and receiver is often called a baby cam.
One of the primary uses of baby monitors is to allow attendants to hear when an infant wakes, while out of immediate hearing distance of the infant. Although commonly used, there is no evidence that these monitors prevent SIDS, and many doctors believe they provide a false sense of security. Infants and young children can often be heard over a baby monitor in crib talk, in which they talk to themselves. This is a normal part of practising their language skills.
The first baby monitor was the "Radio Nurse" in 1937.
Usage examples of "baby monitor".
But if the monitor happened to show white lights for both of them, well, then, what had started out as the Hobson Baby Monitor might end up being responsible for lots of new babies.
Deborah began, then broke off when the sound of crying came through the baby monitor beside her.
With a mother's superhearing, Margo tuned in to the sounds whispering out of the baby monitor beside her.
As Grace sat down, Amanda heard the men talking through the baby monitor.
And it's downright stupid to think a baby monitor would be able to tune in communications from alien ships.
We put the kids in bed, plugged in the baby monitor, and went to the café.