sorted the documentation reads:
App Card is a great way to better represent mobile applications on Twitter and to drive installs. We designed the App Card to allow for a name, description and icon, and also to highlight attributes such as the rating and the price. This will require adding some new markup tags to your pages, which we will cover in this document.
This Card type is currently only available on the iOS and Android mobile clients. It is not yet available on web or mobile web.
