The Userbar module provides an easy way for modules to automatically notify end users about any change in their content status.
The module provides two hooks to feed the content status to Userbar.
1. hook_userbar_info(). This hook provides the list of content status provided by the module. This hook in invoked in the userbar configuration screen which gives the administrator and users an opportunity to enable or disable a sepcific content status.


2. hook_userbar_view(). This hook is used to provide the status of the content for the given user. The implementation must check if the content type provided by the module is selected by the administrator and end user before returing the content status.


For more detailed information on the hook see the userbar.api.php in the userbar module folder.