Baby Monitors
Monitors are necessary gadgets for parents who are out of the hearing range of their children. They faithfully record sounds and images of the infant and allow quick responses from the parents or nanny. Many include dual-radio connections, parent talk-back, relaxing music for the baby to listen to, and a separate video channel.
The predecessors, which served the same purpose, were entirely mechanical in appearance, as seen in contemporary images. They also looked rather frightening.