It's a tip calculator, check-splitter all-in-one app... and yes, there are a bunch of 'em on the store. Check out the demo to see if BistroMath combines the power you need with ease of use you're comfortable with. Ultimately, that's the differentiator in these calculator apps: usability. If you can't quickly split a bill, or split a bill fairly (say some guy ordered a bottle of champagne just for himself), then the calculator isn't for you. BistroMath seems to do this and more quite easily, so if you're in the market for such a calculator -- and yes, some people use these quite often -- check it out for iPhone or iPad for US$2.99. Try not to confuse it with the other Bistromath, which is not in the App Store.