On-Screen Protractor is a simple java application that allows to measure an angle on the screen.
Originally the program was conceived to assess the angle between north and a given point on any map open on the screen, therefore the background of the application window is transparent and the angle is measured from the positive y-axis and clockwise. The application allows to move the origin of reference axes and to rotate the axes as needed.
Great little app, just what I was looking for. Is there a way to hide the X and Y axis and just show the two radius lines that I'm using for my measurement?