Well, this could be done with a script. A basic idea of how it would work: You would loop (with a sleep break in between), and on each loop you would ls -l the folder, then count the resulting lines. When the lines are greater than the default number, a file has been added, and you can do what you please with that file.
Something like the pseudo script below should get you started in the right direction.
Code:
while (infinite)
sleep X
VAR = $(ls -l /path/to/folder/ | wc -l)
if VAR > 1 # default number of lines in an empty folder)
print
move
fi