There's also a feed for workspace activity, but there's no link in OpenGoo to reach it. We will add for next release.
The url for these feeds are something like this:
All activity: http://<opengoo's root>/index.php?c=feed&a=recent_activities&id=<user id>&token=<user token>
Workspace activity:: http://<opengoo's root>/index.php?c=feed&a=project_activities&id=<user id>&token=<user token>&project=<project's id>