If I were to implant an RFID tag inside a human brain, can I receive the correct signal from outside the skull?
The short answer is that I don't know. I have never heard of this being done. I would say that it might be possible to read the tag, assuming the transponder were implanted just inside the cranium. The passive low-frequency (LF) RFID tags used for implants would not be affected by the water in human tissue, but they would only need a read range of a few inches. You'd need to conduct some testing on a cadaver to be sure.
—Mark Roberti, Founder and Editor, RFID Journal