A photo app designed specifically for concerts - The main feature is that the display goes dark while filming/snapping shots. As someone who goes to a lot of shows, I hate the myriad of tiny squares I see between myself and the stage and I've noticed a fairly small percentage of folks actually check focus/etc., they just stick their phones in the air and shoot away.

Bonus points for good social media integration - Read my location/4sq to know what show I'm at - Easy posting to 4sq/FB/Twitter/Compuserve.