An automatic scribbling machine sounds less than useful, admittedly, but it’s really just the style of line created by this motorized drawing machine. It’s reminiscent of ASCII art, in which heavier characters are used to create darker tones; in this case, the more jiggle added to the drawing platform, the more ink is put on the drawing surface. It’s kind of mesmerizing.
Check out the video (there’s another here):
It’s put together from mostly off-the-shelf parts (Arduino-powered, naturally), though it’s far from simple. The process uses vector graphics and turns it into a tone map, and given a known starting point for the pen, it “prints” by moving the pen along rows and adding jitter to darken the “pixels” to whatever degree is necessary. It looks like it has about four discrete tones it can make — not the greatest range, but in aggregate it works quite well.
You can read how it was put together at the creator Alex Weber’s blog, and he has also put the source, documentation, and so on up on Github.