If you intend to use a shell script ...
#!/bin/bash
httpd_init="/etc/init.d/httpd"
check1="$(pgrep -f httpd)"
check2="$($httpd_init status | grep -E is[^not]running)"
[[ -n $check1 && -n $check2 ]] && echo "httpd is alive!" || { echo "httpd is dead!"; $httpd_init start; }
exit $?
This script performs a simple check on your httpd pids (using pgrep) as well as a small regex check on the response string of "/etc/init.d/httpd status" (which, in case of a service failure, will be "is stopped" of course).
If the service is dead, the script will bring it back to life.
Hope this helps!