@solderandchaos Lots of interesting links posted in response to you question :)
It's not a "pager" per say, as bidirectionality is one of the core feature, and there is no infrastructure as in Pocsag, but have you looked at Armachat? https://hackaday.io/project/183657-armachat-pico-compact-long-radio-messenger

By some aspects they are the spiritual successors of pagers, as some of the essential characteristics of pagers (RX only to stay low-power, etc) were due to technical limitation at the time that are no longer obstacles.