For TV Shows I've long used tvrage to keep track of things:
http://www.tvrage.com/mytvrage.php?page=myschedule (that's the link to the schedule, of course it wont work unless you're logged in and set up shows to go there, but yeah). I don't see google's tv reminder feature being that useful but for movies.. that'd be nice. See a trailer in the movies, pop out my phone and set up a quick reminder so I know to look for it in the future.. yeah.