Concussion Detonator

The Concussion Detonator is a gadget used by Batman that attaches to enemies and allows Batman to stun and disorient those caught in its explosion, giving him ample time to dispose of the enemies.

Arkham Origins Incident
You unlock the Concussion Detonator as you progress through the game. After the Lacey Towers Hotel Crime Scene, Batman needs to break into the National Criminal Database. Alfred states that if Batman is to do something so foolish he'll need a powerful non-lethal weapon the Concussion Detonator. Alfred will radio you to let you know it's ready, at which point you can use the Batwing to head over to the Batcave and pick up the Concussion Detonator from your Workbench. After Arkham Origins Incident

It isn't known what happened to the Concussion Detonator following Origins, but since this is Batman's second year of crimefighting the assumption can be made that this may have been a prototype for a newer variant of the gadget but any of these future designs were presumably destroyed by Bane when he broke into the Batcave where he also destroyed the prototype Batmobile.

Batman: Arkham Origins
You unlock the Concussion Detonator as you progress through the game.

Batman can attach this enemies and when it explodes it stuns and disorients any victim caught in the explosion.

Trivia

 * The Concussion Detonator's function in combat was very similar to the Remote Electrical Charge Gun's ability to disorient thugs into hitting each other. It even had the same quick-fire controls. The main differences were that it wouldn't launch armored enemies into the air, and that there's a slight delay before it activated. It could, however, hit multiple enemies at a time.
 * When first retrieving the Concussion Detonator, it had the same shape as the Glue Grenade. However, when aiming to throw the gadget in combat, it took the shape of a small sphere, similar to the Smoke Bomb. The icon for the gadget was also a sphere.
 * Even though Alfred told Batman that it would be better to use the Concussion Detonator rather than just beating the cops, it could not be used in that way, as you could not proceed through the GCPD Building if there were cops that were still standing, and the Concussion Detonator did not knock out enemies.
 * It's never explained why the Concussion Detonator was never used in the sequel games, whether it was destroyed or discontinued for some reason.
 * The gadget possibly inspired the changes to the Explosive Gel in Arkham Knight, as the secondary use/quickfire behaved very similarly to that gadget. Both were shot in an arc, only attached to one enemy, and took a second to detonate.
 * The Concussion Detonator actually started as a gel-launching function for Arkham Origins, but the idea eventually evolved into its own gadget.