I recently had to deal with this ... introduced a location app without any additional notes to the review, and the application was rejected. In the rejection notification, I was given instructions on how to create a video application in action, and then indicate the link in the review notes.
So, I used another iPhone to take the video, put some body of the explanation in the video using iMovie, upload it to YouTube, put the link in the reviewers notes, resend the application, and then approved 5 or so days later.
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