Does anyone know of a good mileage calculator app for smartphones? Ideally it should be something localized that doesn't require accessing data service except for weekly updates.

I have an iPhone and didn't find anything particularly useful on the App Store so I came up with my own table of routes I usually fly and have "indexed" miles to quickly add up. I suppose one could simply download the UA app (or whatever airline of choice) and check your mileage statement--but that still requires accessing data over the air. I use this as a "planning tool" to figure out routes and mileage...