Ultrasonic Bat Beacon

Batman has devices that sends out an ultrasonic signal that attracts bats. A swarm of local bats then approach the area or target.

History
Batman originally kept this gadget in the heel of his boot. It was used to distract a SWAT team sent by Commissioner Gillian B. Loeb, when Batman was trapped in a condemned building.

Background Information and Notes
Writer Frank Miller first conceived this idea in Batman #406, released in April of 1987.

Movies

 * Batman Returns (1992) - the device is portrayed as a black remote, pulled from Batman's utility belt at the end of the film. The device is activated by the Penguin and the bat swarm is released from the Batskiboat, causing him to fall to his death. This was originally the intended way for the Joker to be defeated at the end of the first film, but technical limitations at the time prevented this.
 * Batman Begins (2005) - a similar scenario is shown to the escape from SWAT in Batman #406. This device is also stored in the heel of his boot, but the lights are red.
 * Batman: Year One (2011) - the famous scene where the device first appeared is faithfully adapted in the animated movie.

Video games

 * Justice League: Heroes (2006) - the device is thrown at enemies as a super move.
 * Mortal Kombat vs. DC Universe (2008) - One of Batman's "Heroic Brutalities" the device is portrayed as a special Batarang that emits large visible purple signal waves.
 * Injustice 2 (2017) - Batman can summon some a swarm of robotic bat-drones with neon blue lights, that surround him and hit the opponent.