I have used www.cjb.net since 4 years ago
I like very much this service, and i think it's a very good service (it's very quick in refreshing dns and it gives short domain name as YOURDOMAINNAME.cjb.net)

The only problem is that nobody use it and routers producer prefers other dynamicdns services (also in openwrt!!)

So i make my script for updating cjb dns

root@OpenWrt:~# cat /local/script/cjb-update

#!/bin/sh

# logger Checking cjb ip
 USER="YOURCJBUSERNAME"
 PASS="YOURCJBPASSWORD"

 if [ ! -d /tmp/cjb ]
 then
    mkdir /tmp/cjb
 fi


 if [  -f /tmp/cjb/cjbip ]
 then
        past_ip=`cat /tmp/cjb/cjbip`
 else
        past_ip="first"
 fi

 current_ip=$(ifconfig ppp0 | grep "inet addr" | awk '{print $2}' | awk -F ':' '{print $2}')

if [ ${past_ip} != ${current_ip} ] ; then
   exec wget -q -O /tmp/cjb/cjb.htm -q "http://www.cjb.net/cgi-bin/dynip.cgi?username=$USER&password=$PASS" 2>&1 &
   echo $current_ip > /tmp/cjb/cjbip
   echo $(date) -- $current_ip >>  /tmp/cjb/cjbip.history
   logger Update $USER.cjb.net to Your IP $current_ip
   rm /tmp/cjb/cjb.htm
fi

after created that file (you can put it where you prefer or call it as you like), you have to set it executable

chmod +x /local/script/cjb-update

Now there are 2 ways to proced or both if you prefer

1- use crontab for scheduling script (ES every 5 minutes)

2-if you use ppp to connetc to internet, you can call script from /etc/ppp/ip-up

#!/bin/sh

sleep 20
logger new connection updating cjbip
/local/script/cjb-update &

NOTE i used sleep 20 becouse script have to wait a bit after ppp connect (or somethimes it try to update cjbdns to early)

any suggestions is appreciated

Yeah dude!