For every SlideShow distributed & viewed, we keep metrics. You are able to see the metrics for SlideShows you own.
In the iOS app, once a user has selected a SlideShow in their list, the History & Activity of that SlideShow can be viewed. This would show any applicable emails of users that have viewed your SlideShow. This give the user a view into who is viewing your content and the overall viewing metrics of that SlideShow. Access the following screen by pressing the metrics button in the top right of the application (looks like a graph icon).