Tiny Rebel Games LLC has released their Doctor Who title for iOS, Doctor Who: Legacy. It is available free on the iOS App Store (though the game is free, it does have in-game purchase options (i.e. you can purchase "time crystals")). The app is an universal app designed for both iPhone (and iPod touch) and iPad and it requires iOS 6 or later (therefore it will not work on the original iPad).
The following is their description of the game: