How can growl be used with syslog?
According to man syslog.conf, Mac OS X's syslog.conf can handle messages only by writing to a file, sending to a remote host's syslog, and send them to users' consoles.



Your best option is probably to send to a file, and write a daemon or a periodically running script that consumes this file and calls growlnotify with what it reads from the file, something like the following:

#!/usr/bin/env bash
while read line
do
    /usr/local/bin/growlnotify "Your App" -m "$line"
done &lt; /path/to/file
echo -n &gt; /path/to/file


Either keep this running all the time by wrapping in a loop, or start it every few seconds using a launchd job and the StartInterval directive. man launchd and man launchd.plist can help you here.