

An easy answer is pagers in hospitals. I know it’s because they’re simple RF technology, and work reliably in cinderblock buildings. But given how advanced so much of our medical equipment is, you’d think there would be a different system. Granted, that system would almost definitely need updates and have potential downtime/crashes, which you cannot afford in that kind of environment
The one I worked at was a very large modern university hospital (in the US) that handled a large part of the states patients. We used pagers in the Emergency Room for code red patients. Many doctors also still use them