ADDandy wrote:the Easiest way i can think of without extra/expensive hardware is to try and send lots of information VERY quickly, more or less hoping that at distance the SNR will make the transmission not work. once you are nice and close, the SNR is good enough that the highspeed communication Works, and thus opening the door.
And why not just ask the radio chipset what the power level is? I have never seen a radio chipset that you couldn't just ask for SNR or RSSI levels from. And I know that I can get the bluetooth signal strength on my laptop and and android phone. I would imagine that there is something similar for rfid chipsets.