The Good Guys are running a promotion when buying multiply Google Nest smoke alarms. I am unsure of the expiry date for the promotion and the battery version might not be legal in all states/territories.
Discount is applied at check out.
Single price is $189.00
Buying 2 15% off - $321.30
Buying 3 20% off - $453.60
Buying 4 or more 25% off - $567.00
My Google Nests are not exactly reliable, especially when the WiFi signal isn't great (it will not tell you it lost connection, it will just randomly malfunction). I wouldn't trust my life to their technology. It will probably read you out a Wikipedia article about fire if it detects smoke, or recommend 3 nearby undertakers.