Since the Event Log was introduced in v4, WPf2b has had the concept of "events"; I needed a way to store in the database what had happened that caused WPf2b to be involved, and I used a simple bit field. Fortunately, event "classes" were there from the start.
Eventually WPf2b ended up with a clearly-defined set of class-based events, and, for the first time, the v5 documentation details them all.
Using a very simple API (hook the name of the event, get passed an instance of EventData), Premium users can now run whatever code they'd like when an event occurs.
If there are any new events you'd like WPf2b to catch, or you think there's a problem with the existing ones, or anything else related - follow the "Comments" link (top right corner) to the Forums and let me know.