Hi Pete -
Were you able to make any progress on this? We are wanting to migrate to Xamarin, but do not see any RFID support in the Xamarin EMDK.
The integrated RFID capability on the TC51 is NFC only and you can implement NFC tag reading using the Xamarin component detailed at Android.Nfc - Xamarin
We have no support for NFC in the EMDK for Xamarin currently so you will need to use generic API's such as the one suggested above.