MTN-55

The Motion Sensor is a usable gadget in the game Battlefield: Bad Company and Battlefield: Bad Company 2.

Overview
An integral tool for scouting and collecting real-time intelligence, this portable high-tech device is designed for sensing even the slightest twitch of movement, alerting the owner when an enemy has breached the premises on foot or by vehicle. They can be thrown much like a grenade to help spot enemy infantry and vehicles in its radius. They operate for a short period of time, after which it will no longer detect enemies.

Battlefield: Bad Company
In Battlefield: Bad Company's singleplayer, on the 6th mission, the player starts with motion sensors, along with an M9. In multiplayer, it is used by the Recon class in Battlefield: Bad Company, who can carry 2 of them at a time. When thrown, any enemies within the area of effect will appear as a red dot in the game world as well as inside the mini-map. There is no limit to how many can be thrown at a time; it is common for them to be spammed, as they can be replenished at ammo crates.

Battlefield: Bad Company 2
The Motion sensor returns in Battlefield: Bad Company 2 with many changes. It is still only available to the Recon class and the user can carry 3 of them at a time. The motion sensor displays enemies within its detection radius on the mini-map as red triangles, and has a shorter active time. Only one of them can be thrown by a player at the time, and if another is used while the first one is still active it will be replaced by the second one. However they now also send out a beeping noise whenever an enemy is detected, alerting the user - and their target. They can also be replenished by ammo boxes from assault players, and resupply very quickly.

Enemies killed within the range of a motion sensor give the player 20 'motion mine assist' points, with 10 extra points if the kill was by a squadmate. Many snipers using all-kit weapons 'spam throw' them to find enemy players and close in for an easy, close range kill.

Trivia

 * It should be noted that when a motion sensor is thrown, it makes a sound when it hits the ground. Hearing the tell-tale 'clink' will tell you that you have been spotted and should take some sort of action.
 * Standing still will not alert the player of their presence (looking around, aiming, using weapons and crouching are not detectable either). This may throw the enemy off, thinking that you have left the area or been killed.