Diatom design studio are developing an open source drawing robot kit that they hope to sell for just $70 dollars. The kit: "Piccolo", will be powered by an Arduino board, and supports movement along X, Y or Z axes. You can attach a pen, pencil, brush or possibly even an X-Acto knife and it will draw out any sketch you upload to it. They plan on including Arduino and Processing libraries that will allow you to develop dynamic drawings using sensor data. In the video below the prototype draws procedural tree sketches that vary according to the bots proximity to a light source. The kit isn't available yet but on Diatom's website you can sign up now to their mailing list.