Nice timing, I submitted a calculator app to QA a few days ago. I'll update this post when it's available (it should appear as "Ala Advanced Calculator"). It's a command line-style calculator, but it also keeps the function count so low that the buttons aren't horrible to use. (Square root is a waste of space, btw, because it's the same thing as ^0.5) The non-highlighted buttons have two functions, changed by swiping the keypad left or right. You can also change the button size and UI color to your own taste.