I use the plastic Ortophon guage that came with the Naim ARO. It works really well. I just set up the arm for the tracking weight that I think I want, tweak it by ear, re-weigh - its usually within a gnats whisker of where I started, mark that with a felt tip pen, and its fine from then on. Non ferrous and low profile. With the ARO the height is critically important, so you have to take the mat off and measure at the record surface height. Can't really see how anything electronic and digital can improve the process.