Is there a way to use a NFC or RFID tag to trigger a device?  for example, I would like to add a tag near a lock and use my phones NFC function to read the tag and pass a message to the eisy to unlock the door which is already controllable through the eisy.

I've recently started using NFC tags... they are wonderful. 

Not sure if you're in the Android or iOS camp, I use iOS.  Using iOS you would need to use the Shortcuts app to create an automation for NFC tag, the action in the NFC tag needs to use IoX's REST API to do something... (such send the node a command). 

I'm currently using NFC tags with HA instead of ISY, I once knew now to build a REST call for the ISY in the iOS shortcuts app so i know it can be done.  I don't see my notes on that anymore tho.  It occurs to me the issue I had at first was with passing Basic Authentication but I ultimately figured that out.

A tip I learned from a youtube video was to build the actual "action" first as a shortcut, get that working, and then set up the "automation" to just recognize the NFC chip and run the shortcut already created.   Doing this makes sharing to another device easier, because the shortcut is shareable (although not as simple as it should be) and the automation is not shareable.