Make *nix automatic re-spawn a process/service if stopped

To make your *nix system automatic re-spawn a process/service if stopped ~

Write a shell script to check for presence of a service and start it if it is not running.
Then attach that shell-script to a cronjob running at frequent intervals.

Example Script to monitor Apache HTTPD web server and start it if is not started ~

#!/bin/sh
pids_=`ps ax | grep /usr/sbin/httpd | grep -v grep | wc -l `
if [ $pids_ -ne 0 ];
then
     echo "Apache is running"
else
     echo "Apache was stopped. Starting..."
     apache_start_=`/etc/init.d/httpd start`
     if [ $? -eq 0 ];
     then
         echo "Apache Started Successfully"
     fi
fi
#############################

 this simply checks for HTTPD process to be present and re-spawn the service in absence of even a single process thread.

There is a wonderful Ruby utility "bluepill" to achieve the same solution in a more advanced and comfortable manner. Cover it sooooon.....