Question: Automatic heat/cooling regulator

Ello!
I live in a hot part of Australia, and as we get more into summer, I've been thinking about trying an automatic temperature controller in my tank.
I'm getting my first lotl tomorrow, and at the moment the weather isn't too bad. The max I've seen my tank is 23 deg C, and lowest 19 deg C. This is without an external fan blowing on the top.

I found this on ebay: ATC 300 Digital Water Chiller Aquarium Temperature Controller W Timer | eBay
and am very tempted to buy one to try it. Has anyone tried these and are they worth getting/reliable?
In a few more weeks, our weather is due to hit the high 30's - 40's. (95-104 F). My room gets very hot - I have a fan, but I cannot install air conditioning.
Also I work full time, so there's 9 or so hours a day that I cannot monitor my baby.
Currently the tank is sitting on a half inch thick sheet of polystyrene foam, which I read can help insulate against heat.
Thanks in advance

Having looked at the product you have suggested it is a thermometer with an alarm that connects to a heater/cooler system. It doesn't have any actual heating or cooling sytem itself.

If you buy a proper chiller (and you're talking $100s) it should have a thermostat built in.

Thanks for the help
I'm picking up my new baby in the morning, and to play it safe I'll use the frozen bottle technique until I can save up for a proper chiller. My sis-inlaw has offered to check the temp for me on hot days until I can upgrade which is a big help.
I looked at the prices of chillers, ouchies! They will be a good investment for my baby's health though