Spawning mobs every x amount of steps a person takes?

[Astal]

Would this be possible using emus perl scripting?

Like an old Final Fantasy RPG. Every so many steps a random NPC type is spawned.

Would it also be possible to add arguements to make it so they only spawn if another npc isnt near, or sometimes 2 spawn ect...., or so only the group leaders steps count towards spawning npcs, it could get messy if each player in the group spawned em.