My idea is that command blocks should be able to target a player that passes through a pair of coordinates or is within a radius of the command block. Maybe it could be something like "kill @c 10" to kill someone within 10 blocks of the command block. This would be helpful for setting traps and/or keeping mobs or unwanted players out of certain areas of creations.
It's already in minecraft. First, pick which players it should scan for, @a for everyone, @p for nearest player, or @r for a random player. Whoever is reported by the variable will be checked if they're within the radius. Now, add arguments.
Let's say you used @a. To set the center, find the x y and z of the search center, and the radius that they should be within. If you got x: 0, y:1, z:2, and radius is 5, then do @a[0,1,2,5] And finally, put this into a command block: testfor @a[0,1,2,5] and lead a comparator out of it.
Thanks for reading,
Pwbriney
Let's say you used @a. To set the center, find the x y and z of the search center, and the radius that they should be within. If you got x: 0, y:1, z:2, and radius is 5, then do @a[0,1,2,5] And finally, put this into a command block: testfor @a[0,1,2,5] and lead a comparator out of it.