PEAR::Net_Growl

Growl is a MACOSX application that listen to notifications sent by
applications and displays them on the desktop using different display
styles. Net_Growl offers the possibility to send notifications to Growl
from your PHP application through network communication using UDP.

MacOS XのGrowl向けパッケージのようです。へぇ。OS Xにはこんなアプリが載ってるんだ。