Better Administrator Access - "Administrator Mode"

Ubuntu should have a clear "Administrator Mode" usable by any user, but with the allowable passwords not tied to the user account. This way, regardless of which user is logged on, the administrator could enable "Administrator Mode". Then an applet would appear in the system tray warning the user that the pc is now running in administrator mode, and you have full access to the system etc. The admin can specify the legnth of time for the mode to last, and can end it at any time.