Lengths is an on-screen ruler.
The application works both in the International System of Units and U.S. Standards.
The grid can not only work in actual size for centimeters and inches, but also it is possible to set the scaling factor to make it possible to measure distances on a map, as intuitive as laying them on the screen and dragging your finger on it.
Watch the following video to see the application in action.
http://youtu.be/pr_oukyOdfg