Spawn mob at x,y,z on timer

I like using spawn cages, but dislike that players can see them, and that they spawn only when a player is close by.

What would be ideal is a plugin that would let me set a mob spawn point with a frequency and variance. So I could say something like:

/spawnloc mk name mob_type x,y,z [frequency in minutes],[variance in minutes]

where frequency and variance would have default values if nothing was entered.

There would be /spawnloc ls and /spawnloc rm to admin the locations, too.

 

That would be awesome for world events on RP and RPG type servers. Please if this is possible someone make it so ^_^

 

Hmm, I also need this for my fake hell chunks
Ghast won't spawn there automaticly 8)

 

I'll bump this