Microsoft just released the My Server 2012 R2 application at the Windows Phone Store



From WP Central:

The app helps keep you connected to your server resources through Windows Phone devices. You can manage users, devices, alerts, and access shared files in Windows Server 2012 R2 Essentials. This is the first version of the app, so let the team know if you have any feedback.

  Microsoft releases My Server 2012 R2 for Windows Phone 8