It would be interesting to compare how RFID tags are integrated in other ERP systems, such as Epicor or Dynamics NAV (both popular .NET-based proprietary ERP products).
Here are two possible options. I’m not sure what to call a serialized instance of a stock item, so I’ll call it a “serial number master” until someone can correct me. 
Also, as I understand RFID technology as typically used in warehouses, it is an inherently statistical process, there is no guarantee that all the RFID tags present will be captured and reported, and there is also a limit to the number of tags that can be captured (and therefore, for example, a limit to the number of DVD players that can be in a pallet).
Option 1 - simple location tracking. Add “RFID tag number” and “last observed location” fields to the serial number master and import the current location of a stock item via the ERPNext API whenever the stock item is “seen” by an RFID scanner.
E.g. Scan a pallet of DVD players on the shipping dock, take the list of RFID tag serial numbers that are returned from the scanner, look up the stock item serial number for each RFID tag number, then import the location (I.e. “shipping dock”) to the serial number master.
Option 2 - location-based transactions. Use the location of an item to make appropriate transactions. I haven’t thought this through, and am even thinking it’s less viable as I write, but as an example, scan a pallet of DVD players that were just manufactured as they are being moved by forklift to the finished goods warehouse. All the serial number masters could be transacted from the WIP warehouse to the finished goods warehouse, based on their physical location now being the finished goods warehouse.
I think this is most viable for medium-value items, where the added unit cost for RFID tracking is not significant, and the statistical accuracy of the RFID system (99%? 99.9%? 99.99%?) can be accepted. I’m not sure if this applies to sheets of punched cardboard for example (very high-volume and low-cost), but perhaps it could be practically applied to pallets or lots of finished cardboard boxes. Tagging high-value items may be useful for other reasons, such as stock control where the inventory counts are assisted by RFID tags.
By the way, can anyone offer typical costs for RFID tags and scanners?
Dale
P.S. Fwiw, I met someone using a customized Epicor system to manage servicing the air-conditioning systems they sell and install in big trucks. The air-conditioning systems monitor actual hours of operation and also air pressure on each side of air filters, and electronically report the data back to the Epicor system when a cell-phone data connection is available. Leads are automatically created for the sales team based on the data from the field units. I don’t see why this sort of customization wouldn’t be equally possible using ERPNext, and without the user and feature-based pricing of a proprietary ERP.