Leo has been the watch model for TAG Heuer in the last several months of Outside Magazine. Not sure if thats the one you are talking about though because I don't remember what he's wearing in the movie. This is what he's wearing in the ad. If you can afford that watch I'd appreciate an i7 and an appropriate motherboard for finding it for you
At 4:25 into the movie I paused it on his watch. Only see half of the watch (well, closer to 30%) and I saw "automatic", and "swiss made". Figured that was pretty common and wouldn't get me too far, but I googled that anyway and tagged on Inception. Found TAG Heuer Carrera Automatic WV211B.BA0787 with steel case, steel bracelet and black dial. Good news, its quite a bit cheaper!