Finally got Hud Lite working this morning. It should be considered a companion for you desk phone.
It has its own web site at: www.hudlite.org
The trick to making it work is that your devices should all be named SIPx where 'x' is the extension. Also, use your deskphone's extension and SIP password.
The default HUD Lite server password is 'password'. To change it see this post: http://www.hudlite.org/modules/newbb/viewtopic.php?topic_id=14&forum=1
HUD Pro is only available if you have a Fonality PBX. Apparently it only works with Asterisk 1.09 at the moment. It would be nice if they allowed you to purchase just HUD Pro but I guess they are counting it as one of their PBX's competitive advantages. It is a nice looking product and seems to work very well.