@Atztecphoenix - there shouldn't be a problem with the scale. Even an old Laserjet 4000 can print at 600 DPI. The mouse chip can resolve movement at 800 dpi on any surface (apart from very reflective) using very clever digital signal processing, so the scale is almost immaterial. You could just chose a surface with a fine texture and use that. All that for a £1 or so (English money). But just gutting an optical mouse, and putting it in an IP65 box would work. http://pickandplace.wordpress.com/20...optical-mouse/