Many devices support ModbusRTU communications. With the ModbusRTU driver you can use AdvancedHMI with more devices than just PLCs.
I successfully tested this with and AutomationDirect temperature controller (SL4824). I used the AutomationDirect USB to RS485 adapter (USB-485M) to connect a PC to the temperature. After changing a few communication settings in the temperature controller, I was able to display Set Point and Actual Temperature in AdvancedHMI.
Soon I will test this with an AutomationDirect servo drive to see if I can control a servo without a PLC.