If GPS's were to be banned, I would think that all electronic devices would have to be banned for carryon use. GPS devices are built into cell phones, watches, PDAs and mixed in with all of the stuff that can attach to a laptop. I just can't see the nice TSA people examining every device to see if there is a GPS included with it.
"I am sorry sir, but this Braun shaver could have a GPS in it" Into the confiscation bin it goes.
True enough, although I do not know how well those devices would function in an airplane. But assuming they could be made to work in a plane, that would present a real problem to the TSA.