Interestingly enough, the hammock does make a little sense, as in the event of a crash the forward momentum would be converted into rotational momentum (considering that its a forward crash and not a side crash, and that the material can handle the forces) there was actually a prototype made long time ago for babies that was like a capsule that would close and spin, the baby would have been dizzy but safe, no idea what happened to that prototype. The string though its absurd as it would be a whiplash for the poor kid