This trigger should be based on the playback of the MainMedia.

Here is how I did it for the flash version, though if you have another idea I'm open to suggestions:
Media emit events as they play (every 100ms). SnuTime's setup registers a listener and compares its time against the media's. If the timing is right, the trigger then emits its own event. korsakow-Events listen for events from their triggers and execute their rules when this happens (if their predicate passes, moot for now).