Google posted on several blogs yesterday an update on app indexing which includes how tos and some stats.
Here are two interesting stats:
(1) For signed-in users, 15% of Google searches on Android now return deep links to apps through App Indexing.
(2) In the past quarter, Google has seen the number of clicks on app deep links jump by 10x.
Google then documents four steps to monitor app performance with deep/app indexing:
(1) Give your developers access via Webmaster Tools so they can display errors in indexed pages within apps, show weekly clicks and impressions from app deep link via Google search and stats on your sitemap and much more to come.
(2) You can see engagement with your app such as weekly clicks and impressions update to the Message center in your Webmaster Tools account. Track how much traffic app deep links drive to your app using referrer information - specifically, the referrer extra in the ACTION_VIEW intent. And coming soon, integration with Google Analytics.
(3) Do not block resources, this may prevent deep and app linking from working properly.
(4) New Android App errors now show content mismatch, Intent URI not supported, APK not found, No first-click free and back button violation errors.
It seems to me, at least for now, Google is going full steam ahead with App Indexing. Will it last? I think it depends on if they can release it with iOS.
Forum discussion at Google+.