Wikipedia
Zello
Zello is an application startup located in Austin, Texas, behind the creation of Zello applications. The applications are push-to-talk (PTT) walkie-talkie for consumers and business and available for Android, iOS, Blackberry, Windows Phone, Windows PC, rugged mobile devices and two-way radios. Zello is free while the Zello@Work application is free for up to 5 users.