Considered by the Batman of Zur-En-Arrh to be the most valuable object in his utility belt.

History

Silver age:

Originally, the Bat-Radia was created by the scientist Tlano, the Batman of Zur-En-Arrh. It's purpose was to discharge electronic molecules that caused a controlled disturbance in the atmosphere. This rendered useless the motors of jet-cars used by Tlano's fleeing enemies. Although it was only effective in the atmosphere of Zur-En-Arrh, Tlano gave the Bat-Radia to the original Batman as a keepsake of one of his most bizarre adventures.

Modern Age:

During the Batman R.I.P story line, the Bat-Radia was re-introduced as a simple Am/Fm radio Batman modified to send a signal giving him control of Arkham Asylum's security systems.

Other Media

The Bat-Radia also appeared in the animated episode of Batman: Brave and the Bold - "The Super-Batman of Planet X!"