Although it’s not a new concept, you can’t deny that it is awesome. The Keerbot is a wall drawing robot. By hanging on 2 known-length strings, the Keerbot uses stepper motors to shift from left and right, and move up and down by contracting and letting out string on either side. While moving a pen/marker/drawing aid makes lines of art.
In some of the demos I see the guys working on getting a spray paint fixture to work. That could be more interesting than just dragging a marker. Currently the guys are using vector art, and known CNC utils to generate g-code. Very similar to how one would do laser cutting/CNC/and 3D printing.