With Office 2010 Mobile, you have also SharePoint Workspace Mobile. To remind you, SharePoint Workspace is the evolution of Groove client (Office 2007) which allow you to keep SharePoint content available while offline.
If you publish your SharePoint site through UAG, you have few additional settings to set.
Once you have added your SharePoint site as application on your UAG trunk, if you don’t do this, you will have: It’s not possible to establish a connection. Try again or contact the site administrator.
To allow SharePoint Workspace Mobile to reach your SharePoint site through UAG, go to the SharePoint application settings and edit it
Go to the Portal link tab and enable Allow rich clients to bypass trunk authentication as well as Use Office Form Based Authentication for Office client applications