Good question. I did a quick search and found:I wouldn't be surprised if they were using a private API the App Store reviewers missed and if this was shot down by Apple. I don't know of any other app allowing screen sharing on iOS. Well, I'n not going to pretend I know the millions of Apps on the App Store so I am happy to be enlightened. Any other examples out there?
Squad – A video calling app for iOS with screen sharing features (iThinkDifferent article)
Squad - be together (App Store)