Unless the game has been designed with touch-screen (or tilt) controls in mind, moving around in mobile game is often an exercise in pain and frustration. So much so that I want to find the man/woman who first invented the virtual d-pad and set their hands on fire.
Not to worry. There's always the GameKlip, a rig that lets you pop in a smartphone (sorry, Android only at the moment) and use a DualShock 3 pad to play a game with.
Priced between $15-23, it looks like a damn fine investment for more complex games like Grand Theft Auto.