I was at the mall recently with my 3 year old, when we saw a little girl about his age wearing one of these harnesses and her mother holding the leash (is there another word?). My son was asking a bunch of questions as to what he saw and why the little girl needed to be on it. I just told him that his Mommy wants to keep the little girl safe.
I've never used one, and never plan on using one of these. I don't think they're too popular, since I don't see them that often.
What do you feel about these? Have you ever used one with your child?