OK, this is flat out amazing. Cowacca is a small strap and ring for kids to hang onto. It just clips on your belt, or backpack, or stroller, or wherever you need it to not lose a kid.
It is made of maple and leather. It was designed by Ono Rinao for a 2005-6 exhibition, Codo Mono Coto, which is a tricky Japanese way of writing "Kids Stuff." It was a design show about living the kid-included lifestyle.
Cowacca is still available at AssistOn, or you can rig your own, because now that you see it, it is the most obvious thing in the world.