Never Back Down -- Basically, it looks like The Karate Kid for the MMA generation. Nothing innovative, but probably some fun for a couple of hours.
This, on the other hand, is a David Mamet movie called Redbelt. So it's probably reasonably good. It's got some real martial arts star power behind it too. Randy Couture appears, and it looks like one of the fighters might be one of the Gracies. Mamet, who knows his tough guy movies, is a BJJ grappler so he knows the moves. You might also glimpse Tim Allen (Yes, Tim the Toolman) in the trailer too. Don't quote me on this, but I thnk I heard he's a BJJ guy in real life too. I don't know about the movie. It just goes to show you never know who's doing what with their time.