One cool thing that someone pointed out is the Processing language. This looks like a very cool thing that I’ll have to play around with. According to their website:
Processing is an open source programming language and environment for people who want to create images, animations, and interactions. Initially developed to serve as a software sketchbook and to teach fundamentals of computer programming within a visual context, Processing also has evolved into a tool for generating finished professional work. Today, tens of thousands of students, artists, designers, researchers, and hobbyists who use Processing for learning, prototyping, and production.
One of the projects they pointed to is the “Poorman’s Oscilloscope.” This project uses an Arduino as the analog front end and Processing as the display back end. I think that with a little thought and programming you could also create a simple spectrum analyzer and make your own waterfall display. (I’m thinking that I could perhaps write a Mac version of Argo with Processing.)