I have recently written two XMPP related things. The first is a prosody module called mod_post_msg which accepts messages in a HTTP POST, using HTTP authentication. It was inspired by this ejabberd module by skeltoac, but it takes full stanzas, whereas mine just takes a plain text message body.
The second is a sendxmpp like Bash script based on cURL which works with the module. It is supposed to work like sendxmpp, but doesn’t support all of it’s options. You can get sendxmpp-curl here.
This allows you to post simple XMPP messages from CLI (like sendxmpp), with less round trips than a full XMPP session would require (At least I hope so).
OpenPGP Key
Pastebin
Pixbox
MMN-o