vertical /horisontal wacom-tablet 'hack'
as you properly know using a ruler can produce perfect vertical or horisontal lines. By chance i stumpled over a hack that can be used to do the same without any AR tool.
This may or may not work with your tablet.. :/
Try to place the pen outside the drawing area and then 'draw'
If it is placed to the right or the left of the draw-area a perfect vertical line is drawn.
independent of how you move the pen. Placed on the tablet 'framing' in top or botton a perfect horisontal line is drawn.
This is a fast and simple way to get straight lines :) -and ofcause it works in any graphic program, not just AR.. doh..
I would have liked to have seen a Wacom tablet with a "drafting machine" attachment...or at least a T-square and triangles...and french curves...for drawing clean lines at various angles and shapes.