This eBay seller currently has a few offers on Xiaomi with one of them being "Buy 1, Get 2 Free". You can select any 3 products from this link and get 2 items free based on the lowest price.
For example buying 3 of the Xiaomi Mi Temperature and Humidity Monitor sensors will set you back $19.95 AU stock delivered. Making it excellent value compared to my recent Hekka deal shipping from China.
Edit: Temp/Humidity Monitor out of stock, Charger still in stock.
These monitors will display the current temperature/humidity and can be linked with other Xiaomi smart home products via the Mi Home app. It also has a "baby monitor" mode where it will send you an alert through the Mi Home app when the temperature and humidity go too high or too low.
For those who are into tinkering there is a custom firmware project for this too.
New seller? Seller only has 11 feedback items in their profile.