Speaking of nalgenes; new helmet design

[tvashtarkatena]

New football helmet

[kurthicks]

or this one!

http://www.getoutdoors.com/goblog/index.php?/archives/2148-Madillo-Folding-Helmet-Video.html

[catbirdseat]

That's an interesting concept. It relies on friction of air escaping a bladder to provide cushion. It gives a more linear shock absorbing function than foam. Pretty interesting, but I'd bet it's hot, but not any hotter than foam.