Hi @Webclan, I have been emailing @Dawn_SD for her opinion on the Arnia system; thanks for the suggestion. Just for your own clarification, in Australia we have 4G and 3G networks - it is the 2G network that has/is being shutdown. The Arnia works on both 2G and 3G networks. I'm currently waiting for them to clarify what frequency bands in the 3G spectrum the device works on.
Those graphs above come from a different, simpler, monitoring system that I connect to via bluetooth. All winter last year my hive was typically low to mid-20s, occasionally 20s, as monitored by the same device.. The temperature drop is just a little sooner than I was expecting, but perhaps given that the other day was our coldest May day in 4yrs I shouldn't be too surprised.