DOMAIN SENTRY - $199 (including 2 years registration where needed)

.au domains must be renewed every 2 years and once expired anyone else can register it. Domain Sentry can watch your domain, warn you when it is about to expire, and automatically renew it if you forget.

Once you have placed a Domain Sentry on one of your domains, we will monitor the domain, and we will advise you as you expiry date approaches. You then have the option to renew the the domain, either through us or another registrar. If the domain gets within 7 days of the expiry date, we will begin our enhanced contact routine.

Domain Sentry could save you $30,000
http://www.smh.com.au/articles/2003/01/13/1041990215929.html

This will involve our staff sending you a fax and a letter by post, as well as calling any contact phone numbers we have for you on a daily basis until we have established that you have been made aware of the upcoming expiry.
If for some reason we are still unable to make contact with you and the domain reaches its expiry, we will then renew it if it is registered through us or transfer/renew it if it is with another registrar.

The price is just $199 for 5 years of monitoring and includes the cost of one renewal if necessary. The service will be terminated at the end of 5 years, or if you request it, or once we have renewed the domain as part of the service. The fee is not refundable or transferable for any other service.