Here we are, my first Iphone application; it is a tip calculator. But not the kind you are punching numbers in by keypad. Instead you rotate the wheels to change your numbers and make calculations. There are 2 wheels in total: Left for changing service (% for tip), Right for changing total amount. You can also split the total amount by person. For that another kind of wheel, the horizontal wheel. If you are struggle with  rotating a long time for a large amount, just hit the setting and change the sensitivity. It will increase or decrease as you wish.

Go and grab it Here