I have found on this forum so far only one possibility:
Here are 433MHz wireless temp readers.
This one is $20 and supports -40°C
But I haven’t found any USB dongle yet to receive the data. Also it seems to work on Linux only.
it would be nice (and logical) for the gateways to store those values for a while, if the PC/Tablet is offline or there is something wrong with the internet.
15sec reading = 24 * 60 * 4 * (4+8) byte = 70 KiB / sensor / day
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