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I recently read an article about a Texan student called Andrea Hernandez who refused "wearing" an RFID tracking tag at school. I became interested in the subject.

Apart from any legal/social/religious discussion, which is definitely off topic, my question is hardware & privacy related.

The short question is

How can we use short-range technologies to track people movements and how precise can we do?

The long question is

I know that if you want to track where a person goes in a wide area, you can ask him/her to install a smartphone application that records GPS track and has the highest accuracy.

I know that if you want access control to a facility you can secure its entrances with contactless badge readers so you know who enters and who exits the facility. This is what many companies do.

If you want to know in which room anyone is, first idea is to secure all doors with the same readers above.

In the past years I read a few articles about ePassports being able to be read from a middle distance (1 to 3 metres) with a special-crafted skimmer so I started to hold mine in an aluminium foil instead of hammering it. I also saw a demo of a bomb, tested on a puppet, that activates itself when scanning a specific passport (see video at around 3:20 for the show) but at a very short distance.

With reference to current NFC/RFID technology, how precisely can we track movements of a person in a facility without explicit scan by user? I mean, is it feasible with today's technology to put scanners on walls and know who's inside a room? If it was Bluetooth or Wi-Fi it was surely feasible but they use battery power

and finally

With reference to the San Antonio case and the fact that a number of schools are hitting the newspaper's first page (even in my country) for adopting "tracking students and/or teachers with NFC/RFID", I would like to ask if what our local papers call "tracking" only means tracking enter/exit from facility or tracking how long do you stay in classroom/bathroom/dining hall...

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Currently this RFID tag advertises a 20 metres range. It features an autonomous power source that is not a battery.

So part of the answer is yes, with today's technology we can mount RFID readers on walls and tell how long do you stay in the bathroom, but nothing to see with passports (they collect power from reader)

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