The Wii U version of Injustice: Gods Among Us doesn't support the iOS companion app. After receiving a copy from Warner Bros., Siliconera couldn't sync up the Wii U game with the iOS app and confirmed with Warner Bros. that the functionality is not present.
The Injustice iOS app launched in April and is available as a free download, a hybrid fighter and collectible card game that allows players to unlock content in the console version of Injustice: Gods Among Us and vice versa. The Wii U version of Injustice: Gods Among Us displays a move list on the WiiPad while you play and also allows players to move the action from the TV to the WiiPad through off-TV play.