It's about a dude called Gary Faulkner (that's Cage) who is visited by God (played by Russell Brand) tasking him with going to Pakistan to capture Osama Bin Laden. This is a real film and the trailer is right here.
It looks absolutely insane, and comes from the director or Borat and Bruno - though this isn't framed as any kind of mock documentary. The craziest part is that it's actually based on a GQ article from 2010 because Faulker is a real guy who did attempt to track down Bin Laden more than 10 times.
Perhaps the most batty thing - Faulkner was seeking Bin Laden in the right place more than a year before he was finally killed by the American military in May 2011.
One Man Army is going straight to home video in the States, there's no word of an international release date.