App to take pictures and add an audio description?

I don't know of any app that would do this at the time the photos are taken.
I do know of a few that can do similar after the fact, like a post production edit, but the result in the end would actually be a video with your photos as a visual and your narration as the audio.

My current favorite is YouCut, by InShot.
It is free, easy to use, and does not put a watermark on your finished product.