The Batwave was an alarm system created by Batman.
After Batman became an outlaw thanks to the efforts of Lew Moxon he could no longer rely on the police to give him information. Because of this Bruce Wayne invented a computer program that was connected to every security system in the city, which he called the Batwave. A giant bat would flash orange on the Batcomputer and would make a loud noise. This would tell Batman of any crime happening in Gotham City. After Batman's name was cleared he and Gordon went back to using the Batsignal.