Optical finger mouse - useful for robots?

I just came across this product, which is an optical mouse that you
strap to your finger.  What made me think about robotics is the
possibility that it may be more tolerant in regards to the distance to
the ground.  The pictures clearly show it being used so that the mouse
is at least 1/4" from the surface.  However, people who make
advertisements have been known to produce pictures that have nothing
to do with reality. I have not personally tested or even seen this
product. Cost $20

http://www.xoxide.com/logisys-optical-finger-mouse.html

Joe Dunfee