And this note in launchpad seems to confirm:gnome-activity-journal is a graphical user interface for Zeitgeist
Zeitgeist is a service which logs the user's activities and events (files
opened, websites visited, conversations held with other people, etc.) and
makes the relevant information available to other applications.
It serves as a comprehensive activity log and also makes it possible to
determine relationships between items based on usage patterns.
This package contains the GNOME Activity Journal, a graphical user interface
which shows a journal of your activities.
- mikeZeitgeist itself is no longer being actively developed. The engine has reached a mostly stable state and is still being used, so if you want to work on third-party plugins that should be fine.