멀티플레이에서 플레이어가 다른 플레이어를 쫓아갈 때 쓸 수 있을 것으로 보입니다. 싱글플레이에서는 자기가 갔던 길을 알아내거나 돌을 다른 돌로 변환시키는 용도가 있겠네요.
/summon FallingSand ~ ~1 ~ {Block:redstone_block,Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:/fill ~ ~0 ~1 ~ ~-20 ~1 redstone_block},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~3 ~1 stone},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~4 ~ command_block 0 replace {Command:fill ~ ~2 ~ ~ ~-24 ~1 air}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:/scoreboard players reset @a walk},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:/scoreboard players reset @a walkSmall},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:/scoreboard objectives add walk stat.walkOneCm},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:/scoreboard objectives add walkSmall stat.walkOneCm},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~3 ~-13 ~-1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ detect ~ ~-1 ~ stone 5 setblock ~ ~-1 ~ cobblestone 0}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~3 ~-12 ~1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ detect ~ ~-1 ~ stone 0 setblock ~ ~-1 ~ stone 5}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~4 ~-11 ~-1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ detect ~ ~-1 ~ gravel 0 setblock ~ ~-1 ~ stone 0}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~4 ~-10 ~1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ detect ~ ~-1 ~ dirt 1 setblock ~ ~-1 ~ gravel 0}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~5 ~-9 ~-1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ detect ~ ~-1 ~ dirt 0 setblock ~ ~-1 ~ dirt 1}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~5 ~-8 ~1 command_block 0 replace {Command:/execute @a[score_walkSmall_min=700] ~ ~ ~ detect ~ ~-1 ~ grass 0 setblock ~ ~-1 ~ dirt 0}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~6 ~-7 ~-1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ detect ~ ~-1 ~ end_stone 0 setblock ~ ~-1 ~ gravel 0}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~6 ~-6 ~1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ detect ~ ~-1 ~ sand 0 setblock ~ ~-1 ~ end_stone 0}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~7 ~-5 ~-1 command_block 0 replace {Command:/execute @a[score_walk_min=1000] ~ ~ ~ scoreboard players reset @a walk}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~7 ~-4 ~1 command_block 0 replace {Command:/execute @a[score_walk_min=700] ~ ~ ~ scoreboard players reset @a walkSmall}},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:gamerule commandBlockOutput false},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:"fill ~2 ~-2 ~ ~7 ~-2 ~ redstone_block"},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:"setblock ~2 ~-1 ~-1 command_block 0 replace {Command:/fill ~ ~ ~1 ~6 ~ ~1 stone 0 replace redstone_block}"},Time:1,Riding:{id:"FallingSand",Block:command_block,TileEntityData:{Command:"setblock ~2 ~ ~1 command_block 0 replace {Command:/fill ~ ~ ~-1 ~6 ~ ~-1 redstone_block 0 replace stone}"},Time:1,Riding:{id:"FallingSand",Block:stone,Time:1}}}}}}}}}}}}}}}}}}}}}}}