OK, situation is as follows:
Ipaq allows you to press 'action button' along with any other button. 'Action button' is when you press the whole keypad down. That way if you, for example, move your character to the right, and you want to jump, you will have to shift your press from the right side of the keypad to it's center. You can't press any of the 'normal' buttons together with keypad directional buttons.
Amigo allows any two button presses in the same time. That way, for example, you can go to the right and shoot, but you can't go diagonally and shoot.
Casio (all models) allows any number of multiple button presses.
> What handheld computers allow more than one button to be pressed at ounce
> and which ones don't.