I've only been within spitting distance of a slot machine a couple of times, but I'm under the impression that pushing a button is the standard way to start the wheels spinning today.

Honestly, you're going to look pretty foolish doing such an arm motion with your iPhone in public. Not a problem at home, though. I actually have a bit of this issue with the quite good MotionX Poker. I feel a little bit goofy playing it in public, sitting/standing there shaking my iPod touch to roll the dice. Oh well.