As I was playing around my iPhone settings a couple of days ago, I discovered a few options I had never seen before. I might be a little late and maybe you guys already know about that but I'd like to share these findings with you anyway.
These hidden features are in Settings > General > Accessibility. While they would appear useless to most iPhone users, they are very helpful for people with hearing or vision disabilities. I know for sure I had been in this area of the settings before but for some reason I didn't notice them all.
Note that these features may be available for iPhone 3GS users only. Also note that when you try to grab a screenshot by of these features in action, it simply doesn't work, which is why I took these bad pictures...