Update Manager Indicator is an Ubuntu appindicator that shows up on the panel when there are updates available and comes with some extra features like showing a list of updates in a submenu, refresh the repositories or display NotifyOSD notifications when you have new updates.
There hasn't been a new Update Manager Indicator release in a while and the previous one was kind of buggy in Ubuntu Precise, so I've packaged the latest version from GIT and uploaded it to the main WebUpd8 PPA. The new version brings GTK3 support, an option to display the number of updates in the indicator icon and a new optional feature to upgrade in the background (until now, you could only use the Update Manager).
To install Update Manager Indicator in Ubuntu 11.10 or 12.04, use the following commands:
sudo add-apt-repository ppa:nilarimogard/webupd8 sudo apt-get update sudo apt-get install indicator-updatemanager
By default, the Update Manager Indicator icon shows up only when there are updates available. To run it and open the preferences (e.g.: the first time, so you can configure it to always display the icon, etc.), run the following command:
Update Manager Indicator is very customizable: you can enable/disable displaying the number of updates in the appindicator icon, enable/disable the notifications, change the upgrade behaviour (using Update Manager or in the background) or change the check interval from its preferences.
To launch Update Manager Indicator on startup, open the Startup Applications dialog, click "Add", enter "Update Manager Indicator" under "Name" and "update_indicator" under command. Note: if you were previously using Update Manager Indicator, change the executable name in Startup Applications to the new one (previously, it was "UpdateIndicator").
Report any bugs you may find @ Launchpad.
If you're using GNOME Shell, there's a similar tool for the GNOME Shell top bar - see: Update Indicator For GNOME Shell Displays New Updates On The Top Bar