The Rewind Say Again on a marine VHF, makes itself very useful when you distractedly hear an important message, but you do not understand its meaning and you want to listen to it again. Or in an emergency phase when the person requesting help is not in a position to repeat the message that was perhaps of vital importance.
It was introduced for the first time by Cobra Marine in 2007 on the F80B model, patenting the technology under this name.