<RANT>
First of all: with all due respect, that is not a good answer and is one thing that drives people up the wall about Mac users: they think command line has no use. If someone is going out of their way to ask for a command line utility, they probably have a good reason. Batch files, access over ssh, etc. GUI isn't ideal for every situation.
</RANT>
As for me, I found this page via Google trying to find the answer to the same question.
I travel for work and would like to be able to use the command line to set/change my call forwarding number remotely via ssh... VNC is a PITA over slow connections. With a command line utility (in this instance I'll call it "modemdial"), I could go any machine on the internet and set my call forwarding like this:
ssh my.ip.address
login: My_login
password:
******
Welcome to my.ip.address!
judolphin> modemdial *73,5551234#
And my home phone would be forwarded to 555-1234.
Would be somewhat cool, don't you think?