The Pip-Boy is a wrist computer worn by all the vault dwellers and it has a multitude of uses.
Vault-Tec created the Pip-Boy in the pre-war times and it became a staple of every vault dweller.
It is used to interface with many of the vault mechanisms such as the doors to other vaults and the door to the surface.
A technological Swiss army knife
It can be used as a map, as shown when Ma June enters Moldaver’s coordinates into Lucy’s Pip-Boy so that she can take Wilzig there.
After Lucy cuts off his head, she retrieves a tracker from her Pip-Boy and sticks it inside Wilzig so that she always knows where it is.
It also comes along with an inbuilt torch that Norm and Chet use while searching through Vault 32.
When Norm investigates how the surface door to Vault 32 was opened, he discovers that it was opened from the outside using his mother’s Pip-Boy, even though she had been dead for many years.
Barb is seen using one of the earliest versions of the Pip-Boy and Cooper links it to the listening device so that he can spy on the Vault-Tec meeting.