Haven't gotten chance to read all the posts but I just always wondered ... Why doesn't someone make a trackpad/touchpad that fingers can be used on and also a stylus for signing documents/drawing etc.?
I've always tried using the eraser end of pencil and other random things to get the touchpad on my computer to respond but it doesn't seem to pick up anything but fingers. At the same time a glass touchpad or something would be great but if we could use a stylus on it at the same time would be great!
The eraser end of a pencil doesn't "transmit" (sorry, I'm not english) current, so it won't be able to do that. Nor would a piece of wood, unless soaking wet, or your hands if they're overly dry for that matter.
A piece of metal will do, however it would need a certain area to be covered, so you'd need a flat end piece for that too pointy and it won't work.
I think of track pads as "passive", whereas stylus-controlled pda's etc. as "active".
Anyway, even if you wanted an "active" one, there would be no need for glass whatsoever. It's superfluous.