DynDNS

#
# USER = Your DynDNS User Account Login-Name, Sample fred
# PWD  = Your DynDNS User Account Password, Sample K2KS-82h
# KEY  = Your DynDNS Update Key, see Settings in your dyn Account
# HOST = Your Full DynDNS Hostname, Sample me.dyndns.org
# IP   = The new IP your want to resolve HOST to
#

Alternative http

wget --quiet --output-document=- --http-user=$USER --http-password=$PWD https://members.dyndns.org/nic/update?hostname=$HOST\&myip=$IP

Alternative https

wget "https://$USER:$KEY@members.dyndns.org/v3/update?hostname=$HOST&myip=$IP"