How to get an ssh tunnel started every time my Mac boots?
OK, no sooner asked than I figured out the last few pieces.
To get ssh to do what I wanted, here is the shell script to do what I want:
#!/usr/bin/env bash

echo $0 run on $(date)
# Just chose an arbitrary 401 value range of random numbers.  
randport=$(/usr/bin/python -S -c &quot;import random; print random.randrange(5555,5955)&quot;)
remoteport=$randport # this way we always know what port we are using.  Fix other problems later... 

portfile=/Users/rcook/.ssh/linode_remote_port.txt

echo $remoteport &gt; $portfile
scp $portfile rcook@linode.richcook.net:
ssh -N -n -i /Users/rcook/.ssh/id_rsa -o ExitOnForwardFailure=yes -R $remoteport:localhost:22 rcook@linode.richcook.net &amp;

sleep 5
while ps -Awwx -o &quot;user pid ppid pcpu pmem comm args&quot; |  egrep -v grep |  egrep &quot;${remoteport}:localhost&quot;; do
       echo found
       sleep 30
done
echo finished at $(date)

I put the launchctl script into /Library/LaunchDaemons/Tunneler.plist.
This way it loads at system launch.