Everyone is talking about the upcoming mobile friendly ranking factor coming up on April 21st for the mobile search results - but what is live already today as a ranking factor in Google mobile search is App Ranking.
Google announced with the mobile-friendly ranking signal that Android Apps will rank better in mobile search, when the user is signed in and has the Android app installed - assuming the app does app indexing.
Google wrote back on February 26th:
Starting today, we will begin to use information from indexed apps as a factor in ranking for signed-in users who have the app installed. As a result, we may now surface content from indexed apps more prominently in search. To find out how to implement App Indexing, which allows us to surface this information in search results, have a look at our step-by-step guide on the developer site.
This was overlooked for good reason:
(1) They grouped it with the mobile-friendly web site announcement.
(2) This only works for Android users that have your app installed and are signed in when searching.
(3) It only works with Android apps that have a web site counterpart and can use App Indexing.
Until Google makes App Indexing work with (a) iOS and (b) apps that are standalone without web site content to match their app content, then it won't really be much of a factor for the majority of searches, in my opinion.
Either way, this is a great way for those of you who qualify for this to get great mobile ranking for your app in Android mobile search today.
Forum discussion at WebmasterWorld.