Once it was loaded up, a challenge was sent to the person playing Watch Dogs on the PC. The challenge was accepted, and the PC player had to finish whatever his mission was, as the tablet player was sending the cops to stop him. The tablet player is able to control where the police chopper goes by simply dragging his finger around on the map, and this was reflected in the actual game in real time. He was also able to direct cop cars, and at one point he caused the PC player to smash his head on into one of the many road blocks that players will be able to pop up from the ground.
All told, it's definitely a cool way to merge a core experience with the mobile platform. While the demonstration was neat, I have to wonder how engaging the companion app will be when you're not in the same room as the other player. Sure you'll get experience points and whatever else through the mobile app that can be applied to the main game, but we'll see how interesting something like this can last when all you're seeing is a map.
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