There's been a couple of attempts at visualizations in the past, namely Ironcope and VUmeter. May be worth contacting the devs of these to find out if any changes can be made to make them customizable, i.e graphbars, sinewaves etc. The next bit would then be to integrate the final product into a mediaplayer. There's another app that's available, can't remember the name of it. It displays a circle and a line that resonates when sound is picked up via the microphone. Some of the effects available were a bit too heavy for a stock N900 and were just barely useable with a big overclock. *Slightly off topic* Now to find out where to put that font for use in Theme Customizer.
19:48 <Remi-X>: my name is fry and im shy 19:48 <Remi-X>: sh*t how can i even say something that dumb