I can see the Biologic Pango folding helmet's appeal for short haul commuters needing to stash their kit in a very confined space. Substituting the industry standard thin polycarbonate layer with ABS (a thermoplastic) greatly reduces the likelihood of scratches and other accidental damage that comes from banging about in all manner of luggage but contributes to its portly 509g – about the same weight as my first hard-shell lid 25 years ago.
While dragging the parents around the south island this week, I noticed a French Canadian guy folding up his bike helmet and putting it into his backpack. I remembered that ages ago Dahon had advertised their "Pango" so I said hello and had a look. Labelled "Biologic", it was indeed the Dahon folding helmet and very impressive it was too. If anyone's interested it's available from the Biologic site for about $130 and looked really sturdy. Great for commuting I'd imagine.