As U.S. Army troops eagerly look for new gadgets, on the commercial market,  with possible usefulness on the battlefield, military labs are actually developing some stuff that appears to work. Especially if batteries are not required. One of the better ideas is STF (shear thickening fluid). Unofficially its called liquid body armor. When applied to Kevlar cloth, it prevents a knife or ice-pick from penetrating. STF does this by reacting to a sharp pressure, and stiffening. One of the vulnerabilities of Kevlar has always been knives and similar sharp objects, especially when dealing with lots of hostile civilians. STF wont be ready for troop use for another two years.