This application works based on tracking the change of the Autodesk® AutoCAD® system variables value. After you turn on the tracking mode, whenever (in real time, including when command is active or done) the program detects a change of any system variables, it will print at command-line the value before and after change immediately to show you.
Of course, this app does not apply for the system variables that always change value in real time. e.g.: DATE, VIEWCTR...