TestWindow opens a window on any public screen. It does nothing except report it's size and position in the screen's titlebar. As dull as this may sound, it's actually useful at times when you want a window's dimensions and/or position to be just-so.
Future Plans: There are a lot of bells and whistles that could be added, such as default text in the window (font-sensitive, of course), or a secondary window that displays the position and size in editable gadgets. Development of TestWindow is slow, however; it isn't a project that I give a high priority to.