LinuxNOV posted a guide about updating manger extension for Gnome Shell on Ubuntu 11.10
Update manager indicator notify you with available updates for the system. it shows up on the top panel of gnome shell interface with how many updates available, update name, brief information about the update and the size for each update.Update Manager Extension For Gnome Shell On Ubuntu 11.10 Oneiric Ocelot
From the update manager indicator menu your can click on update to get latest updates from added repository and you can upgrade them directly from the menu as well. Also you can adjust the refresh interval between each time to check for updates.