Someone gifted us a jumper-- the kind that you attach to a doorway. I don't know much about them, but they seem like a death trap. (Although my husband examined it and tried to explain how the physics of it are actually quite sound). Now I know that these (and exersaucers, etc.) aren't great to have kids in for extended periods of time, and that wouldn't be my approach. But from a safety point of view, are these actually safe? My instinct says no, but I don't have any facts to back this up.