The qualifier is needed, because what is simple now was complicated even five years ago. For example one similar project that might serve as Euphonopen (with no pen) is David Rokeby's Very Nervous System which he built for the first time in 1986, an amazing achievement at the time. His machine was made for generating sound while dancing - and drawing is a subset of dancing - and could be adapted for certain kinds of big drawings. However VNS, like the present Euphonopen, is very subjective: the sound it generates is based on what sounds good or interesting to David Rockeby. I would love to devise a piece for a drawing performer and VNS.
The present Euphonopen, nicknamed the EuP, is made for drawings that are page size (16" x 20") and it generates a set of parameters 72 times/second, that can then be programmed to generate sound. Its hardware is a Wacom tablet with a pen, a computer and speakers. It has possibilities, but the sound is only as interesting as we make it, so this is why a composer is indispensable at this stage.
Sha Xin Wei offered to have some of his grad students build other EuPs, which might not be using pens, to digitize the drawing movement, that is the dance of the drawing hand and generate sound. How interesting the sound would be remains to be seen.
Meanwhile "nulla dies sine linea" - not a day without a line - as the convict said, adding another stroke on the wall on which he kept count...