Use the terminal IP address.
You could solve it a few different ways; here's one.
Use the activeX MEIPInfo to read the last number of the IP address (IPOctet4), on the startup display.
Use the Remote Display Number in global connections to open a pop-up (that never closes) of the same number. Ex. IP address is 192.168.1.174 and it would open display number 174.
On the pop-up display use the activeX MEMacro10 to write any heartbeat you want to your PLC.
You will need a pop-up display for each IP address, and each pop-up is coded to write to different tags in the PLC.
It will be a pain if you want to change or add IP addresses as you will have to update your project. But at least you only have 1 project to maintain that works for any terminal.
Getting fancy, you could even hide/show different screens based on the IP address. That lets you have just 1 project for different panel stations; which makes maintenance easier as there is only 1 project file. No need to worry about getting the correct file for a specific station.