The bash-completion script can deduce which options are supported by an application by parsing the output of --help and of usage lines. In Bash.

http://anonscm.debian.org/cgit/bash-completion/bash-completi...

Either way, it might be neat to do it dynamically, so command-line programs could be turned into guis live by typing "guify xyz".

The gui could have labels with the command options, and upon hitting enter they could close and send the command back to the command line, so you're learning the commands as you go.