Tunemark Radio visualizer demo from Brian Stormont on Vimeo.
Music in the demo is "Not Hip Hoppie" by Digitube (http://digitube.us)
I'd like to stress this this visualizer will work with any audio stream being played in Tunemark Radio. It looks best when the stereo channels have distinct volume levels.
Also, it should be pointed out that the visualization is not using the local microphone to pick up the audio signal, so will also work if you are using headphones or a dock connector. It's not a responsive as a full desktop-based music visualizer, but this is because the iPhone SDK does not provide access to the decoded data packets of MP3 or AAC audio as they are being played. So, instead, I have to only use the audio chaneel gain status words returned by the SDK.
You can download the app for free from iTunes.