The design is a simple easel-mounted wall-style plotter. A marker is suspended by two strings, each is rolled on spool, which is driven by a stepper motor. The entire setup is controlled by an Android tablet through a IOIO board. The app in this repo (https://github.com/ytai/IOIOPlotter) allows converting photos from the camera or gallery into abstract vector drawings and immediately execute them on the plotter.
More information here: http://ytai-mer.blogspot.com/2013/05/ioio-plotter-and-motor-control-library.html
IOIO-OTG Board is available here: https://www.sparkfun.com/products/12633
IOIO Board on github: https://github.com/ytai/ioio/wiki