If you have an Android app, you'll be happy to hear the latest feature by Google for app developers. Developers will now have the option to get their app content indexed, and that content to be opened up within the app on Android devices. This will help provide a seamless user experience for users when they are alternating between websites and apps.
Googlebot can now index the content contained within an Android app, either through a sitemap file or through Google's Webmaster Tools. This means that if someone searches for content that is contained within an app, and the user has that app installed, they will have the option to view that content within the app, rather than just on a usual mobile webpage. For sites that have content on their main website as well as their app being displayed in the same search results, the app results will appear as deep links within the search listing.
Right now during the testing phase, indexing is only available to an initial group of developers. Signed-in searchers within the United States will start seeing these results on their Android devices within a few weeks.
App developers can sign up to let Google know they are interested in having their apps indexed. Developers can fill out an application of interest at Google but they should be aware that they do need to have deep linking enabled within their app (full instructions for developers on how to do this here). Developers will also need to provide Google with information about alternate URLs, either within their sitemap or in a link element within the pages of the website.
App indexing is only available for Android apps at the time. No word yet on whether it could expand to iPhone or Windows apps as well.