Can a Smartphone read RFID tags from a distance of few feet (NOT NFC)?
Being a bit more specific: I would like to know whether there's a Smartphone that can detect an RFID tag from few feet away using its original HW (no external devices) and OS capabilities. Any comment/direction to reading material will be highly appreciated.
Answer
I think the answer depends on your use of the word "RFID Tag". In the classic sense, a read-only transponder, equivalent to a bar code, the answer is not yet. There are proposals for 2.4 GHz RFID that could use existing WIFI chipsets to identify nearby objects. Nothing standard or accepted is available.
However, based on the application you describe. One potential answer may be to flip how you are thinking of setting this up. If you just need to know if a certian, unique, person is near a spot in the mall, maybe instead of their phone looking for an RFID tag you need a low cost bluetooth sniffer (connected to a low cost computing board) looking for their phone, via bluetooth MAC addresses, within say 5m. As long as the customer has bluetooth enabled, has signed up for your service and your read points are connected to the internet this approach should cover your use case.