The following evil drawing tool is a combination of Zach's stroke example and Memo's fluid library. I previously used it with color tracking through Computer Vision but I decided not to use it afterwards since it was not relevant enough.
Different key presses control whether the stroke is drawn, the Memo texture or both renders. Thanks OpenFrameworks and Memo for making this ouput possible! The source code provided uses version 006 of OpenFrameworks and Memo's ofxMSAFluid library. [download src]