Currently IOS 5 allows you to press and hold the round 'home' button which would - > activate the camera button -> after which you have to press the camera button to -> activate the camera app -> Position the screen to the picture you want to take with your hand -> tap once on screen to focus with your other hand finger-> then move to the hardware volume button or on screen camera picture taking button to depress and take the picture. The above takes 4 steps at least and require more effort from the user to remember and manoeuvre the phone interface.
I would suggest with the jailbreak iphone 4S or future upgrade IOS6 or Iphone 5; you would only need 2 simple steps which require much less effort and time from the user to take picture.
1) Press and hold 'home' button to activate camera app straight away (yes some may argue that undesirable consequences may happen if the home button get depressed accidentally, my counter argument would be with the iphone cover that protects the phone like a 'book cover' would mitigate the risk and the worst case scenario would be some bad pics would be taken which can be deleted easily is well worth the benefit)2) You may still take picture with the volume button or on screen picture button, but remember that the next thing most people do is to focus the image. I suggest tap on the point of the screen to focus the image and without lifting your finger hold the the same point and the picture would be taken. You no longer need to aim at the small on screen picture taking button or the volume picture taking button which is difficult to take picture in the portrait mode or landscape mode for left handers. Summary: Was thinking if there is a phone that allows user to (1) "press and hold" home button to activate the camera application; (2) tap and hold anywhere on screen to focus and take picture. There: Picture taking in 2 steps.