I am interested in having a set of 5-10 wireless indoor temperature sensors in a range between 0 and 30 degrees Celsius that send their data within 10 seconds of measurement to e.g. the cloud which can be displayed on iOS and Android when high priority delivery is enabled and otherwise, it should update every 15 minutes (this would probably save power).
WiFi is available, but perhaps not everywhere. I expect the signal to have to travel through more than two concrete walls in some places, so perhaps it still needs to be connected via either the electrical grid too or some kind of special IoT network with a centralized receiver.
It should be easy to manage that set of devices as one group, name them, etc.
Additionally, the data should be made available in an open, documented format.
Preferably, there would also be some Linux desktop software for working with multiple such time series.
Can anyone recommend a good product?