Google has been indexing Android apps for a couple of years now. According to Google, indexing mobile applications not only results in a better mobile experience of the user, but the developer also sees more installs and better app engagement.
For instance, in Google's screenshot of iOS app indexing, a user can search for a reservation at one of their favorite restaurants. The search results would include a link to the OpenTable application, when if pressed, would take the user directly to the native application.
Google notes that indexed links from an initial group of apps will begin appearing on iOS in the coming weeks through search results in both the Google App and Chrome for signed-in users. Google notes that app indexing for iOS will initially be limited, but it is working to make the technology available to as many developers as possible.