Watch_Dogs Companion: ctOS is an app that lets you hook up with anyone playing the Watch_Dogs game on their console or PC. You can take control of the city in the player's game and do battle with them.

You can deploy a police helicopter and cop cars, and interact with electronic tools in the game to catch out your opponent. You can also set challenges on a player's map for them to complete. 

The app is designed to work over uPlay, PSN or Xbox Live, although connection problems currently persist.