Here's a workaround:

sudo apt-get install mpg321 wmctrl



while [ 1 ]; do z=$(wmctrl -l -p | grep -i 'facebook|miniclip'); if [ -n "$z" ]; then mpg321 myfile.mp3; fi; sleep 5; done

This will play myfile.mp3 if any open current window title matches "facebook" or "miniclip".