xwatchwin 1.1.1-2 (amd64 binary) in ubuntu hardy

 This is to watch a window on another X server. Xwatchwin allows
 you to peek at a window on another X server (or the same server).
 To use it, you must specify the display name of the machine you
 want to watch, then the name of the window on that machine. Very
 useful for demonstrating to a class of new students.