The US Navy just proved a point
You can dive down deep and mash a button and your nifty sub will leap up to the surface in a dramatic manner. Its good training for emergencies, it provides "focus". Unless a Japanese fishing boat full of students is wandering by. Why not take a dull metal or wooden tanto and coat the edge will a thick paint. Allow to dry until it is still tacky and will transfer, but will not drip onto the mat. This way your gi will pay a price for your lack of focus and the attacker will be more confident about pressing the attack than they would be with an edged weapon.