According to the Visualforce Developer Guide, you can specify a different format for a Visualforce page by using the ContentType attribute on the tag. Specifically you can display Visualforce page data in a Microsoft Excel spreadsheet, specifying a value of: application/vnd.ms-excel.
I am following this example here: https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_styling_content_type.htm
This works great in desktop, but does not seem to work in Salesforce1, specifically I get an error message when opening that page in mobile that states, "Unable to Read Document". I could not find any documentation as to whether this truly is unsupported for Salesforce1. Can anyone confirm this?