Not sure about a new iOS 6 feature that does this but what I do is the following.
Hold down the home button and the sleep/wake button at the same time and it takes a still image of what you are viewing.
When you are making a video there is a Photo button in the bottom left corner. Tap it and it will continue recording and will snap a picture. DON'T use the volume up button. It WILL snap a picture but will also stop the recording.
Cheers
Won't that be in reduced quality though? In comparison to a standard picture taken.
I'll never understand people buying products they don't understand how to use.