How about using the iPhone's built-in accelerometer so that the user can enter ball/strike without taking his eyes off the game? Shaking the iPhone up/down (gently!) could indicate a
strike, a quick wave left/right would be
ball. The phone could vibrate to give feedback so the user doesn't accidentally record a pitch without knowing it (long
buzz for ball, several short ones for strike). If it buzzes when I didn't mean to record a pitch I can use
undo (or take the incoming call

). Of course, if I'm keeping the pitching chart I wouldn't use this 'shake for strike' feature, but often I can't see the pitches that well, anyway, and would prefer to keep my eyes on the game -- something you can't do when using a paper scorecard!
By the way, I'm really enjoying using your App as-is! Great job!
Farmer