Well, probably not actually in the works, seeing as the game hasn’t come out yet, but Ubisoft are covering their backs in case they are thinking about it with some recent domain registrations.
Watchdogsmovie.com and watchdogsthemovie.com have both been registered along with other variations of that name. As these have just been registered, it’s unlikely there is a movie set to appear anytime soon. But the premise behind the game is so good, it can’t fail to make a great movie. There is a chance of course that these domains could be used for short movies to promote the game, similar to the Ghost Recon short movie that was recently released. Over the past few years Ubisoft have invested lots of money into movies. So don’t be surprised if we see a film based on the current hottest franchise.