Sorry to say but nothing seems clear with that brand is there really a RFID (if its really NFC: it would solve this) adapter?! (Couldn't find detailed datasheet on the specifics of the adapter used by them)
As you know: Nothing in the sdk, Theres no standardized RFID extension set as that means there is significant duplication among the vendors , but in a ideal world Google would build the needed RFID extensions directly into Android.
I'd suggest you search or post on stackoverflow there are similar questions some are suggesting some plausible things...
But RFID wise your on your pretty much on own with android the only path I see is developing extensions based on common source code if you got skills and time...
Edit: supposedly some manufacturers of RFID adapter ARE providing SDK's for their products maybe there's something's to scavenge from that.
Best of luck keep posting if you got something
Sent from a generic and obsolete desktop kept alive by the evilish powers of free softwares