TipKalc is easy to use. Just spin your iPod’s Click Wheel until your bill amount is displayed in the center of the screen. Everything else is automatically calculated for you. It calculates recommended 15% and 20% tip amounts, grand totals, and even splits the check up to five ways.
Using KolorWheel is just as easy. You select a base color by moving your thumb over the iPod Click Wheel. A suggested color scheme is automatically displayed in the four corners. If you prefer to match your base color to a particular object, you hold your iPod next to it. Again, a suggested color scheme will be automatically displayed in the corners.
More info: http://www.koloroo.com/