The Westpac card with the same service has since ended, so I found the below alternative.
What is Flight Delay Pass?
You register your flight with the Mastercard Flight Delay Pass service before travelling. If the airline announces a delay that meets or exceeds 120 minutes, you will receive a LoungeKey™ pass that provides access to a lounge at the airport where you are delayed. LoungeKey™ gives you access to a network of over 1,500+ of airport lounges worldwide. The service is available to the main passenger (cardholder) and up to 1 travel companion(s) on the same flight.
Regarding children: Each individual lounge has its own policies on the admission of children. To check the policies of a specific lounge, please visit https://loungefinder.loungekey.com/Pass and to read the Flight Delay Pass FAQ click here.
How to get access
You need a Cash Passport Platinum Mastercard, you'll need to add $100 to the card( fee free with BPAY) to order it, according to the FAQ, you can login and withdraw this once you receive the card, alternatively just use it as a normal card. Once you have received your card, you then register your flight via this link: https://flightdelaypass.mastercard.com , if your flight has a delay of 2 hours+ within 24hrs of depature, you will automatically be sent access to the airport lounge (over 1,000 airport lounges & free food included). If flight is canceled, no lounge pass is granted.
So it costs 0.5$?