I made an app called "Foto Lock" which allows a user to choose a photo from their camera roll and disabled the ability to swipe to the next photo -- which would prevent those awkward moments of someone seeing a taboo photo.

Apple rejected it under the guidelines it provided no value or was too simple. I don't have the exact verbiage, but I can get it when I'm back at home.

They suggested I add more features... Yes my app was simple, but it solved the exact problem many people have.

Here's a video of it: http://www.fotolockapp.com/