I achieved something similar in bash, in a terminal-agnostic way a while back. I have this script saved at ~/cdf.scpt : https://gist.github.com/2037421

Then my .bash_profile contains the line:

    alias cdf='cd "`osascript ~/cdf.scpt`"'

Now if I type "cdf" in a terminal window, it will automatically cd to the directory of the front-most Finder window.