It is possible, but not how you would like it to be. You can't play music off an iPod in iTunes (there are a few apps that WILL let you do this - like Senuti). However, if it is your iPod and the music on the iPod is linked to your iTunes library, you should just be able to use coverflow in your library and it will be the same as if you are browsing your ipod.... obviously because the content is the same. Coverflow works fine while you iPod is syncing, too.