What is app indexing?
This feature is possible with: Google Search App version 2.8+ for Android 4.1+, and in mobile browsers on Android if the user is signed in.
App Indexing Adding 24 More Brands
Google introduced the concept back in November, went live in December, announcing that they are, “working hard to bring this functionality to more websites and apps in the near future.” Seems like the concept has been successful, what with the very recent announcement of an additional 24 more app brands which support app indexing. They are:
500px, AOL, BigOven, Bleacher Report, Booking.com, Eventbrite, Glassdoor, Goodreads, Huffington Post, Merriam-Webster, Pinterest, Realtor.com, Seeking Alpha, TalkAndroid, TheFreeDictionary, The Journal, TripAdvisor, Tumblr, Urbanspoon, Wattpad, YP, Zagat, Zappos and Zillow.
Bing is set to launch their own version of app indexing, which they dub “app linking” for windows devices and should be available shortly.
If you are an interested app developer, get more info here : https://developers.google.com/app-indexing/