Twitter Cards, a feature of the micro blogging site which allows tweets to be expanded, has rolled out an extension of its service to include apps, products and photo galleries.

This will be very good news for app developers as their app details, as well as links to the requisite Google Play or App Store page, will be available if a user expands a tweet containing a link to participating sites.

The App Card, which is only available for special approval at the moment and only on Android and iOS mobile clients, allows a name, description and icon of the app on the Card, alongside other attributes such as price and rating if applicable.

The other innovation, announced by Twitter at a developers’ event in San Francisco last night, was mobile app deep-linking, allowing users more freedom to go to an app directly from a tweet.

“With mobile app deep-linking, users will be able to tap a link to either view content directly in your app, or download your app, depending on whether or not they have your app installed,” explained Jason Costa, Twitter head of platform in a blog post.

Twitter’s relationship with developers has been fractious at times. Back in August, Twitter updated its application programming interface (API) to 1.1, with developers needing approval from the micro blogger itself if their apps create over 100,000 individual authentication tokens for Twitter client apps.

Similarly, the Developer Rules of the Road were changed, with Twitter tightening its grip on how third party apps display tweets.

Yet this seems to be a move to appease the developer community.

The markup and code for the App Card is available here. Do you see Twitter Cards becoming a major facet of how people use Twitter in the future?