In 1937, two years after the first Trial of The Century--the Lindbergh Baby kidnapping/murder--had ended, Zenith introduced the Baby Nurse. Used in conjunction with the wireless Guardian Ear, this was possibly the earliest baby monitor around.
The Radio Nurse was the first commercial design by the sculptor Isamu Noguchi, and its biomorphic, abstracted head form is closely related to his surrealist work of the same era. And even though it's supposed to be a nurse, I think it looks more like a kendo mask or a ninja.
Recognized both for its design and historical importance, it's also very rare; a lot of Radio Nurses were smashed during WWII for having a Jap name--Noguchi--on the back. Never mind that Noguchi was American... [Thanks for the tip, Eric!]