monitoring a directory's used space

[Adam Wolfe]

Is there any way to use monit to check a directory's used space?  I see 
options for filesystem and individual files, but I need to monitor a 
directory's size (should be 0B).

Or, failing that, I need to simply know when there are files in a 
directory, then I use exec to place them on a server where clients/devs 
can get to.

Anyone have any advice?  I was using

"check filesystem with path /yada/yada
    if space usage > 0 B
    then alert
    then exec"

and that seemed to work but a "monit status" perpetually shows a failed 
check.  It appears to be calculating the path leading up to the dir I am 
watching.

Again, just need to know when a file or files appear in a specific 
directory (that should always be empty) and then tun an exec.