For this drill we will need at least two students. one starts stationary and looking away from the other student. From time to time the stationary student will turn and see if he or she can catch the movement of the other student before he or she freezes (catching the movement you will advise the student where he was caught so next time you will have a better student to work with and you will have more to work with). This is a great game for children and an even better one for adults who can place more experience into this drill to learn to do the basics well.
As the drill evolves you can create a routine such as the observer turning slowly around so both learn to pay attention to the edges of their vision and to the vision of others. Another way to learn this is to place a large object as a tree or brush between you and see how it works to either advantage or liability.
One last variation to this drills is to place your arms in different ways in front of you when you do this drill. It is always good to know how you are obstructing your own vision with your limbs and to avoid doing so.
The drill is good for one simple reason. You must be good at the basics to do well in it. No technique or fancy gear can do the work for you.