The Dynamics AX Expense tablet app was release for Windows 8 a while back along with a few other tablet apps. This gives mobile users that have Windows 8 tablets a way to administer there expenses and submit them for approval and payment.
This video gives a quick walkthrough of the some of the functionality in the app.
The mobile apps are as they come meaning un-like core functionality with Dynamics AX these apps you can’t modify. Keep that in mind when reviewing the functionality and manage the feature request to see what work around could be done for example if a new field is requested to be captured, purchase you need to use the notes and description fields carefully.