As you know, Google launched the first part of their mobile friendly algorithm in February, which meant Android searchers would see Android apps they installed come up in the mobile search results higher for content within the app that matched their query, assuming the user is signed in to Google and the app uses app indexing, a way of telling Google how to link to specific content within your app.
Well, now the apps do not have to be installed on the Android device for Google to rank the app's content for a relevant query in the mobile search results. As long as an app deploys app indexing and Google finds the query relevant to the content within an app, if a searcher searches on their Android device, the app can be displayed in the search results.
Instead of the user being taken to the content within the app itself, the searcher will be taken to download the app and then to the content. Which to me sounds like a bad user experience (make someone download something to see content).
So this is a huge encouragement for Android app developers to deploy app indexing for their apps, so their apps can rank for a huge array of relevant keywords and the app can get way more visibility than ever before.
Mariya Moeva from Google calls this "a very big deal" as she posted on Google+. She is 100% correct, it is a game changer.
Here is an animated GIF of how it works and I already here searchers saying they see apps in the search results mix that they do not have installed:
Forum discussion at Google+.
