Getting notified by SMS is better than via email, I think, because then you can tell the difference between midnight spam and a server fire. Here's my command for sending a shortened message (to #yournumber#@YourCarrierSMSGateway.com)
Add these to your commands.cfg and then change your contact settings (usually contacts_nagios2.cfg) to use the appropriate command. `define command{ command_name notify-service-by-sms command_line /usr/bin/printf "%b" "$HOSTALIAS$/$SERVICEDESC$ is $SERVICESTATE$ ($SERVICEOUTPUT$)." | /usr/bin/mail -s "$NOTIFICATIONTYPE$" $CONTACTEMAIL$ }
define command{ command_name notify-host-by-sms command_line /usr/bin/printf "%b" "$HOSTALIAS$ is $HOSTSTATE$ ($HOSTOUTPUT$)." | /usr/bin/mail -s "$NOTIFICATIONTYPE$" $CONTACTEMAIL$ }`