The idea behind Periscope is letting people broadcast live footage to any of their Twitter or Periscope followers via a mobile device. Viewers can tap on screen sending a “heart” to show they like a broadcaster’s video or leave a comment via Twitter. By now, Periscope allows users to save and re-share their streams and doesn’t even require a Twitter account to stream video at all.

Source: https://agilie.com/en/blog/how-much-does-it-cost-to-make-an-app-like-periscope