> There is also a new NFC proposal ( again my google fu is not helping ) that allows multiple NFC card / tags to be read at the same time
This is already in standard NFC-A/B, usually just called the 'collision avoidance' or 'select' protocol, effectively doing a binary search over the uid space (iirc) asking particular bitmasks of uids to respond. The main thing is that it used on the reader side, not the (emulated) card side so I'm not sure what the support for multiple emulated cards is like (and if there is a different proposal for that).
This is already in standard NFC-A/B, usually just called the 'collision avoidance' or 'select' protocol, effectively doing a binary search over the uid space (iirc) asking particular bitmasks of uids to respond. The main thing is that it used on the reader side, not the (emulated) card side so I'm not sure what the support for multiple emulated cards is like (and if there is a different proposal for that).