Google Analytics on Steroids (GAS) is a wrapper around the Google Analytics API that adds several useful events categories. One of the most interesting is YouTube. By default, _gasTrackYoutube fires events for play, pause, finish, and error. You can also specify playback percentages. This GitHub Gist is a simple page that shows how to set events for 25, 50, and 75% playback (line 14). Thanks to Eduardo Cereto for helping me get it to work.