Run this script specifying a URL. The script will check the URL every 60 seconds to see if the contents change. If the contents change the script will beep and will continue until aborted.

check_site.sh

function check_site()
{
	local stored_hash=''
	local changed=false
	while sleep 60; do
		# beep a bunch of times:
		if $changed; then
			if [[ "$(command -v osascript)" ]]; then
				osascript -e "beep 5"
			elif [[ "$(command -v tput)" ]]; then
				tput bel
			else
				echo "IT CHANGED!"
			fi

			continue;
		fi

		local temp_hash=`curl --silent "$1" | md5`
		# if stored_hash isn't set, then set it,
		# otherwise check if stored_hash = temp_hash,
		# if they aren't equal, beep to let me know
		if [[ -z "$stored_hash" ]]; then
			stored_hash=$temp_hash;
		elif [[ ! "$temp_hash" = "$stored_hash" ]]; then
			changed=true
		fi
	done
}

if [ "$1" = "-h" -o "$1" = "--help" -o -z "$1" ]; then
	echo
	echo "Usage: $0 [url-to-check]"
	echo
	echo -e "Run this script specifying a URL as the only argument," \
		"\nthe script will check the URL and take a hash of the html" \
		"\ncontents at the URL. The script will check this every 60" \
		"\nseconds to see if the contents change. If the contents" \
		"\nchange the script will beep to alert you."
	exit 0
fi

check_site "$1";