Have you taken a photo with the flash, and found that it was too bright, and the photo didn’t turn out well? Did you wish you can adjust the flash brightness to avoid bad photos?
If so, you'll be interested in Noctacam, an app I built that does exactly this: https://itunes.apple.com/us/app/noctacam/id1240793690?mt=8
You can also see how the photo will look before you take it, rather than regretting after the fact that you missed a shot.
Try it, and let me know what you think. Is it useful? In what situations do you use it? Any other thoughts?