Just stumbled up on this (via TiVoBlog who in turn found it via TiVo Lovers) and will have to give it a try sometime:

From TiVo HME SDK for Python:

An implementation of TiVo’s HME (Home Media Extensions) protocol for Python, as a module (hme.py), a simple server (hmeserver.py), and examples (mostly ported from TiVo’s Java HME SDK). Everything is released under the LGPL 2.1+, except where noted. (Most of the examples are Common Public License.)

I developed this in Python 2.5.1, and haven’t tested it with other versions, but it does nothing exotic. (hme.py depends only on the struct module. hmeserver.py is a bit more demanding.) But I have tested it in Linux, Mac OS X, and Windows XP.