Booktrack is an iPad/iPhone/iPod app that mates a soundtrack to ebooks. Basically, you follow a little arrow down the page, which is supposed to help you sync what you're reading to the relevant sounds.
This might mean music (which could be kinda cool if done right) or it might mean sound effects (I'm trying to imagine Nicholson Baker's House of Holes using this app).
The thing that disturbs me, though, is that this is reading is supposed to paint pictures in your mind. I want the prose to take me places, not someone's idea of what I should be hearing in my head. (I'm not alone in this opinion, either.)
Then again, people said that music videos are evil because they offered pre-determined images to music appreciation.