I know there are a thousand of these available online. This is one I just wrote and wanted to make it a thousand and one. This script will start irssi if there is no irssi process available.
Save the following script somewhere (example /home/kay/bin/irssi_init.sh) and add the following to your crontab:
*/1 * * * * /home/kay/bin/irssi_init.sh >> ~/irssi_init.log
