Project Sword is being developed by Chair Entertainment, which was responsible for the XBLA hit Shadow Complex. It will support multiplayer and achievements via Apple's Game Center infrastructure. We'll have more details on the game as we get 'em.
Update: Cliff Bleszinski has tweeted that a playable demo of the castle environment featured in the Project Sword demonstration is now available on iTunes for iPhone/iPad/iPod Touch. Grab it here.