Jesse posted todo.pl, a command-line interface to HiveMinder (Best Practical's GTD-oriented multi-user task tracker.) It didn't do a few things I wanted (which mostly turned out to be protocol issues) and, well, it was written in perl :-)
I rewrote it in python, keeping general usage compatibility (it currently still uses the YAML-format config file, for example.) It isn't at all complete (partly because the particular features I wanted from the web interface, but-first and and-then weren't reflected in the API) but it can do just enough to consider it "real":
The current version is in flux (as is the protocol) so it may not work
for you - if it doesn't, try again later. It's moving away from
all-YAML (since the old syck python bindings are
broken in a couple of obvious ways
and have been pulled from
the upstream syck sources,
and the new modern PyYAML bindings seem to be a
little too clever. But it should settle out soon - part of the reason
the Old Testament IETF required actually interoperating
implementations was to keep developers honest, and that's working
pretty well here :-)