Offering your choice of common tip calculation methods–percent of the total, percent of the food and beverages portion, or multiple of the tax–this handy iPhone web application makes it easy to enter the numbers with a customized onscreen keyboard. Tap the numbered list of how many diners need to split the check, and the cost per person appears instantly on the screen. A version that runs locally on your iPhone (no Internet connection needed) is available at http://dannyg.com/iphone