Rearmed allows players to control "personas from both Brotherhood and Revelations," sneaking through and killing friends in 4-player online, single player, or one-on-one Bluetooth modes. This game is currently not on the US App Store; IGN spotted it on Canada's.
Assassin's Creed II Multiplayer, by the way, has disappeared from the App Store, allowing Ubisoft to pretend that Brotherhood invented the multiplayer, and that this is an offshoot of that console game. "Assassin's Creed innovative multiplayer is now mobile!" Which is how it started!