In what at first glance appears to be an effort to Undercut Barry Diller's Aereo service, which provides broadcast signals over the Internet to subscribers, ABC announced on Sunday that it will launch an app on Tuesday that will provide live streaming of its broadcasts in New York and Philadelphia to subscribers. The catch: users of the app will have to be authenticated as cable subscribers in those cities. (No authentication is required until the end of June.) ABC said that it plans to introduce similar apps in Los Angeles, Chicago, San Francisco, Houston, Raleigh-Durham, and Fresno later in the summer. Dubbed Watch ABC, the app will allow users to watch most programs live and some -- the number was not disclosed -- on demand. Anne Sweeney, the cochair of Disney Media Networks and president, Disney/ABC Television Group, described the app as a game-changing innovation for the broadcast television industry. The app will initially be available via the Apple Store for users of iPhones, iPads, and iPod Touch devices and from Amazon for Kindle Fire users. A version for the Samsung Galaxy is due later this year.