I've not added any buttons yet though. So I can move the mouse cursor around my screen at a reasonable rate using just a fingernail, but I cannot click on anything without my real mouse.
Using the touch screens I already had made it easy - I knew what library to use to read touch co-ordinates from it. The entire sketch so far is only 33 lines long...including comments and blank lines! All the real magic is happening in the UTouch and Teensy libraries...all I have to do is get the read (x,y) values back from the UTouch library, compare them to the previous set of values, then send the difference to the PC using Teensy's Mouse.move(x,y) function. :)