As I've developed my app, I have imported and incorporated a lot of images, sounds, etc. I guess I could just write a shell script that greps the source code, but I'm wondering if there's an existing that will identify any unused resources in my project.
Thanks!
No, and there can't be since there are ways in which resources may be used without any reference within the app source. The push notification service takes the name of a sound file in your app bundle for instance, so all sound files that are in formats usable for push notifications may not be unused even if there is no reference in the app itself. There are other similiar situations as well.
Obviously you can write some scripts to handle removing resource if you know what is going on, but I would never expect to see Xcode provide anything like this functionality.