Problem:
While trying to access appweb on mobile/tablet browser, I am getting a blank page with following error message:
[ Note : I am talking about app webs for SharePoint hosted apps for SharePoint 2013 and Office 365 -> SharePoint online; I am not talking about office web apps just to clear the confusion. ]
” The endpoint /sharepoint app1/_layouts/15/mobile/authn_dispatch.aspx is not accessible in the context of a sharepoint App.”
created a thread for this at http://social.msdn.microsoft.com/Forums/en-US/appsforsharepoint/thread/98ed1984-7748-41ff-bf04-387a15030168
Workaround
I did not figure out any workaround yet and don’t know whether there is any settings/way to get this working or this is by design?
I will update my findings once I get it sorted.
Please share your suggestion about this.
Update : [added on 13 sept 2012 00:58 AM]
It turns out that Mobile views are not supported for app webs for this *preview*; and so the problem is by design itself.
By turning on desktop view, I managed to work the app webs only with Android’s default browser.
No success with iOS even for desktop view.
I have not tested with Windows tablet yet but I guess it will work there..!!
According to Technet Article: Supported mobile device browsers in SharePoint 2013 Preview
aanuwizard.com 
Hi Aanu – from what we have heard, it is unlikely that SharePoint Apps will be available on the standard SP2013 mobile templates. I have to declare that I work for a mobile software vendor called Azurati, but the reason for responding here is because we recognise that mobile users will want to access Web Parts (in previous versions of SharePoint) or Apps in SharePoint 2013 and have created a concept called V-Parts that allow custom developed Apps and Web Parts to be accessed via Azurati’s secure cross-platform mobile SharePoint solution, called SharePoint2Go.
Feel free to check out http://www.azurati.com and to contact us if you would like to understand more about how we can support mobile versions of SharePoint Apps. We would love it if you were to review our solution on your blog too!