We have quite a few plugin hooks already built in - but they are not documented.
Examples are:
onPublishEvent, OnDeleteEventDetails, onDeleteCustomEvent, onStoreCustomRepeat, onDeleteEventRepeat, onDeleteEventDetails, onEditLocation, onBeforeSaveEvent, onAfterSaveEvent, onSaveTranslation, onEventEdit, onEditCustom, onExportRow, onGetEventData, onDisplayCustomFields etc.
We also have triggers within RSVP pro which are triggered when an attendee signs up for an event etc.