This is an unique material, Kevlar is commonly used as a lining in bullet proof vests.
You're a double 0 agent and on a mission to save the world. In the last critical moments, your facing your arch enemy. A henchman appears from the corner of your eye and begins to shoot at you. It's too late to dodge, the bullet hits you in the chest. You should be bleeding to death right now, but thankfully your Kevlar phone case was in your breast pocket.
Time to continue kicking ass.
By the way, this phone case is probably not bullet proof, so don't count on it saving your life. If you do get shot, go to the hospital.
Kevlar does not reduce the radio signal of your phone. So there's no need to worry about losing reception whilst maintain that unique weave look.