This application performs the basics operations (+, -, x, /) and works with brackets. Its ability to not register previous pressed keys, which makes your results wrong, is its most interesting feature. Try it!
Moreover, it keeps an history of your calculations throughout the whole session which can be displayed and sent by e-mail.
You can also save results as value of two variables, which you can always update.
Very useful to verify long expressions and to get a pdf with your calculations.
The owner disclaims all responsibility by the use of the app gCal.