The Motion Sensor is similar to the Spy Plane. However, it is a piece of equipment, not a killstreak, and it (similar to the Heartbeat Sensor) works in a small circular area rather than the whole map. Allies are not able to see the motion sensor on the mini-map. It can be hacked if a player has the pro version of the perk Hacker, players with Hacker Pro will remain undetected by the motion sensor. Note that the Motion Sensor is not limited by any material or height. The motion sensor does not time out, it remains useful until destroyed, picked up, or when the player dies.
Being a portable UAV means it works almost just like it; it has a short delay between 'sweeps', which could prove fatal to the owner if an enemy is fast enough to avoid it. Its use in Hardcore is limited as its findings can only be shown through the mini-map, which is disabled in hardcore. This can be mitigated by looking at the map on the pause menu.