There is simple way to monitor, transmit, and create alert, (event), with a Arduino and transmit result data with POCSAG. There is a easy experimental way. Using Arduino and RFM22 board, as well you can use Si4432, you can send data on Pocsag QRG 439.9875Mhz Ham band.
I monitor GPS coordinates, temperature, with a DS18B20, and Vcc value, and create an alert if Vcc drop under 5volts.
Data are sended every five minutes, or instantly if alert event.
There is the result with PDW:
Some experimentation’s with small UHF PA, RFM22 board and Arduino UNO.