standard toaster said:
you know thats not to bad an idea.
Some rfid chips are very small such as this
Which may be why you could not find it
I always assumed they would be about this size though
If you were really serious you could even implant it in your finger so you could never get caught.... Im not sure how far away it has to be from the circle so im just throwing things out there
This is very interesting, interesting in several ways:
firstly there are a whole series of different flavours of RFID, frequencies used, size to receivers etc
How they limit the size of the scanning area is usually done by placing the "scanner" in the centre of the target area, and adjusting the power until it gets to the desired maximum range, i.e the size of the circle.
A poorly tuned "scanner" could be quite wild.
this is also influenced by the size of the rfid "chip" and antenna etc that is used, think of ones in stores in books they are quite large etc. you could through several ways mimic the frequency of the rfid chip thats used
(provided that they dont use individual serialized RFID chips on their hundreds - if they did you would need to copy it - this is another whole interesting topic, given it would look like you were betting the same $100 chip hundreds of times

provided that its not encoded in some manner.)
You could have a chip on the end of your finger under a band aid, have some makeup applied to it to look normal, have some latex fake skin over it, wear some funky jewelery etc etc. lots of different methods.
again it all comes down to that "circle" of the RFID scanners range.
This is have no experience on or about. i deny everything.
Cheers
Ringy