Along with the launch of the latest hack-centric title, Watch Dogs, Ubisoft has also released the free “ctOS” mobile app where you can play with friends across two modes, Race and Free Ride, using your smartphone or tablet. In these modes console and PC players are pitted against those using the ctOS app; players in Watch Dogs must race their way to the finish line as ctOS users do everything in their power to stop them by either setting up road blocks, sending in police cars, or causing explosions. ctOs users can not only terrorize their friends, but if they happen to be offline you can join a Quick Match to go against other random people.
Though the app does not directly tie-in to your main Watch Dogs experience it does include its own progressions system and a total of 26 challenges. As you defeat console and PC players in either mode you gain experience to improve your hacking abilities and unlock additional police units, hack and skills. There is also a map generator which allows you to customize the map like where the starting point is, the time of day, and how many checkpoints are on the map.
The ctOS mobile app is free to download on iOS and Android devices and does not require owning Watch Dogs to use!