Funny you should say that...if fishing from a boat (except Mikes..I always forget to take one) I lay an unhooking mat in the bottom of the boat. I always unhook fish whilst still in the water, but like you say, sometimes you need to bring a fish in. In this case, the mat needs to be wet.
I think they are a great idea...if used wet..if dry, they do more damage than if the fish was laying on the grass.
Good post!