Right here.   Basically, it's a vest of goo that is incredibly flexible, yet under impact becomes incredibly stiff, stiff enough to stop a bullet!!

It seems to me to be a type of non-newtonian fluid, like the cornstarch and water slurry (here's a link to a co-host of discovery's Time Warp dancing on it, then tripping, falling, and sinking in it) that science teachers like to make for their classes.
 
Maybe this will be the end of heavy, thick, inflexible, Kevlar and iron plates.  Good for science!!