Hi Chris, your idea about sending an SMS is a good one. Currently this isn't a feature on Sequematic but I have an idea on how to implement it. It would require you to send an SMS to an Australian phone number. Would that be an option for you?
If not, do you have a spare phone at home? You could have your regular device send a text to the other device. Then, that device could trigger an IFTTT applet which would call a webhook (over your home wifi).