I set up the SDR dongle and app on my laptop and played around with it for a few hours. It was pretty interesting to see just how many pagers still seem to be in use. A lot of it seemed to be alerts from sensors of various types - refrigeration and things like that. But the majority looked to be from hospitals. Including what seemed to be patient data.
All the retained and volunteer fire stations around the UK use pagers, because they're simple, reliable, and moderately firefighter-resistant - and about 70 quid to replace when they get smashed, deep-sixed, melted, driven over by the pump, or chewed by a dog. Yes, this week alone.
They're used for alerting rather than paging, in that the message is four flashing LEDs and a lot of beeping rather than a description of the incident, and as such the paging transmitters just transmit a unique number rather than a message. The message is always "get to the fire station right now".
