As I recall, the gauge just helps to set a specific angle for offset or helical. Do you really need one? My guess is no. Where it would come in handy is for a shop with a multi-setup where they wanted to make sure all the jigs were set to the same angle. I have a 3-Bitz setup mounted on a board, but I usually only use one of them when I fletch, so I just set the angle (actually always set at the same angle) and go for it.
I believe they still make them, although you'll never see any place advertise them.