Doesn't the industrial/building automation industry already have solid solutions for your fridge example?
Many buildings already have sensors wired in to PLCs and it's easy to network with the PLC to record and display the signals (for which there are many existing "dashboards" - HMI packages of varying cost and ability).
I don't think it would matter much who owns or maintains the server if you're using a PLC to aggregate your signals onto the network. Many companies are paranoid and would want an in-house server. But it wouldn't be much different to use a cloud based instance.
It's true that existing automation hardware and software are obscenely expensive compared to consumer tech, to the point where renting/subscription might make sense for certain use cases. The systems sufficiently complicated, though, that independent professionals usually manage the setup and maintenance.
Many buildings already have sensors wired in to PLCs and it's easy to network with the PLC to record and display the signals (for which there are many existing "dashboards" - HMI packages of varying cost and ability).
I don't think it would matter much who owns or maintains the server if you're using a PLC to aggregate your signals onto the network. Many companies are paranoid and would want an in-house server. But it wouldn't be much different to use a cloud based instance.
It's true that existing automation hardware and software are obscenely expensive compared to consumer tech, to the point where renting/subscription might make sense for certain use cases. The systems sufficiently complicated, though, that independent professionals usually manage the setup and maintenance.