Are you talking about playing your own music from your iPod while the app is running? I'm pretty sure you can do that if that's what you're referring to.
Other than that, if you want your music to be integrated to an app, that's a whole different story and you might wanna ask a developer of course.
Apple, the all mighty, doesn't allow developers to access the iPod API, therefor no apps dealing with your music is possible at this time. And maybe ever