Is it possible to add Excel service web part in SharePoint 2013 app?
My intention is to create dashboard with graphs and charts (from excel which was published) in the app.
Please help me with any reference links.
Initiate page editing and insert the Excel Web Access web part from the Business Data category. This web part can show either whole sheets or specific named items from the workbook. Just make sure it's under 10MB.
If you use Excel Services REST API, you can request parts of a workbook model and receive their representations in JSON (for complex processing), text (for placement in DIV or SPAN) or image format (for IMG elements). See samples here: Sample URI For Excel Services REST API
The problem with App model would be cross-site scripting protection of the browser that prohibits cross origin resource sharing unless the target web application allows your app's DNS domain to make cross-domain calls to its endpoints.