The Heartbeat Sensor is an attachment featured in Call of Duty: Modern Warfare 2, Call of Duty: Modern Warfare 3, Call of Duty Online, and it also makes a brief appearance in Call of Duty: Ghosts and Call of Duty: Infinite Warfare. It was also cut from Call of Duty: Modern Warfare Remastered. The attachment allows the user to track multiple targets, somewhat like the UAV killstreak. It displays the positions of people who are fairly close to and in front of the player. It also will produce a beep whenever it picks up a hostile target, which will increase in pitch the closer the target is to the user.