Assume you want to create an ssh tunnel somewhere and want to keep it up. cron is your friend here.
Enter this entry into your crontab using 'crontab -e'. homedir is wherever yourhosting provider dumped you.
* * * * * /homedir/boot/BOOT 2>/homedir/boot/BOOT.errors >/homedir/boot/BOOT.log
Create a directory for this. [not required, personal preference]
$ mkdir ~/boot
Create the boot file with these contents:
-----------------------------------
ps ax | grep -q "33306:[l]ocalhost:3306 destination_server"
case $? in
1)
nohup ssh -R 33306:localhost:3306 destination-server &
;;
esac
-----------------------------------
Note, this assumes that the output of a running ssh tunnel on your specific flavor of Unix somewhat resembles this:
6034 ? S 0:12 /usr/bin/ssh -R 33306:localhost:3306 destination_server
This job will run once a minute and check to see if the process is running. If it isn't, it will get fired back up.