A Wattz Electronics C-U model motion sensor. Detects the movement of biological material over a distance of meters using a tuned radar device.”— Fallout in-game description
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.
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.
- It may be sold by Killian Darkwater in Junktown, 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, North-East ) 
- 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 punk boat's general store.
- The AutoMap scanner feature can be used to scan the area ahead and to plan accordingly, despite its need of an active item slot.
- The AutoMap scanner feature can also be used via the inventory.