There is a feature in Windows Phone 7 hidden in Office settings called "office hub". this feature allows user to connect to corporate SharePoint server externally through UAG 2010. I noticed that its not been documented well as how to set this up and what's required.
Windows Mobile Phone site has documented few steps about setting up the Office hub for external users but it doesn't tell you anything more that that. You can review this here:
http://www.windowsphone.com/en-us/how-to/wp7/office/use-office-sharepoint-workspace-mobile
However in terms of setting up things on the UAG side of things , what you need to do it is setup typical SharePoint publishing app or use your existing one and ensure that on SharePoint 2010 server you do setup correct AAM configuration to consume the zones that user through UAG when using external URL will hit and SharePoint should be redirected to the correct site. I am not going to document all this as there is a lot fo resource now available but from old days three blog posts on setting up AAM on SharePoint and configuring UAG server with correct host name are still my favourite that were written by my colleague Meir in the days of IAG. its a three part tutorial that is a great reference to sort AAM configuration and setting up DNS and UAG SharePoint settings. Please review the following blog posts for this :
Part 1:
Part 2:
Part 3:
and finally TechNet UAG SharePoint publishing guide should you need more details:
http://technet.microsoft.com/en-us/library/dd857299
Once External user is now able to access SharePoint correctly from Mobile Phone browser and you are able to launch the office document hosted on SharePoint office library , it means SharePoint AAM and UAG SharePoint application is configured correctly.
Now moving forward we intend to open the office document directly from Windows Mobile 7 Office hub feature. In Windows Phone 7 in Office hub --> click the UAG tab and put the SharePoint portal AAM name that you have setup on UAG <documentation link provided above> .
On the backend ensure that SharePoint 2010 is setup for Forms based authentication.
Please review SharePoint 2010 documentation on how to do this:
First go through this article just to understand as what you are about to do on SharePoint side of things :
Now the better way of achieving this is:
Once SharePoint is setup correctly with FBA , Office hub will work correctly through UAG 2010.