Yes, is under development, but not work properly yet.
How are you developing it? Are you modifying the SQL-entries directly or are you using XMLRPC?
I made a thread couple a weeks ago about a vacation plugin for postfixadmin and they told me I should use XMLRPC instead of modifying the database directly.
I might have misunderstood something though as I'm no good at programming :p
I'm really happy if you get it working because it's the only thing I'm missing from my mailserver