You might want to check into the new line that Spyder is doing. I saw their stuff at Interbike, and it's really cool. The armor is soft and moldable, but on impact it gets hard like regular armor. They actually had balls of the stuff to play with. You could squish it in your hand like play doh, but then when you hit it with a hammer it got rock hard.
It's also intergrated into the clothing, and they say it's pretty breathable, tho I didn't try any of it on.

I found this online in a quick search...

http://www.outdoorretailer.com/or/ph...tylus/8023.pdf