Thinkgeek IdeaFactory Submission Part 2: Music Visualizer
This is a straightforward device: An audio visualizer (represented by a tower of LED lights) that would intercept the audio feed to your speakers from the computer or media player (iPod/iPhone) and display some pretty lights accordingly.
This would operate as visualizer or can become an ambient mood light at the flip of the switch. This can be expanded to be an iOS device dock, and can include a USB Hub to add functionality.
Personally I like idea of a visualizer on my desk for atmosphere, but it is just a cosmetic decoration when all is said and done.