Motion sensor

A Wattz Electronics C-U model motion sensor, or simply motion sensor, is an item that detects the movement of biological material over a distance of meters using a tuned radar device. This device snaps into the Pip-Boy.

Characteristics
If placed in an active item slot, the motion sensor can be used in conjunction with the Pip-Boy 2000's AutoMap feature. The motion sensor will display all living and moving beings on the map – represented as red dots – if the "Scanner" button under the AutoMap is clicked.

In Fallout 2, carrying a motion sensor in the inventory gives a 20% bonus to the Outdoorsman skill when traveling on the world map.

The Fallout: Brotherhood of Steel 2 version would have appeared as a simple device, it "hooks up" with the player character's Pip-Boy allowing them to know where their enemies are.

Fallout

 * It may be sold by Killian Darkwater in Junktown, or the shopkeeper in the Cathedral.
 * At the general store in the Hub.
 * Found in the Unusual Call Box special encounter.
 * In one of the lockers in The Glow (Level 1, northeast)

Fallout 2

 * One can be received as a reward for the Vault City quest Enter NCR and return to Stark.
 * From the armorer in the Navarro Enclave Base, whom must be killed for it.
 * Sometimes sold in San Franciso at the Oil Tanker's general store.