That’s cool, on http://blog.section9.co.uk/2010/03/iphone-rfid-reader.html you can see the work process in pictures. The RFID chip is from http://www.id-innovations.com/new%20launch.htm.
“The idea behind this project is to see what the iPhone’s serial is capable of and to try and have a little fun with RFID along the way. This reader works with the low frequency (125Khz) tags but I have a half working version for MiFARE Hi-Frequency as well.”
“The CATaLOG project aims to track our two cats Bobbin and Tuffin as they go in and out of the house so we can see which cat spends more time outside, what their favourite time to go out is, and also get sent SMS messages if a cat goes missing for a certain amount of time.
The system is designed around the Arduino Microcontroller linked to a low cost RS232 RFID reader and uses the Arduino Ethernet Shield and a Linksys WAP11 router acting as a wireless network bridge to send the data over the internet.”
“Want to detect the presence of RFID readers? Want to control when a RFID tag is active or readable? We describe how to do both using bits of copper and card, and some readily available electronics hardware.”
“This device can do almost anything involving almost any kind of low-(~125 kHz) or high-(~13.56 MHz) frequency RFID tag. It can act as a reader. It can eavesdrop on a transaction between another reader and a tag. It can analyze the signal received over the air more closely, for example to perform an attack in which we derive information from the tag’s instantaneous power consumption. It can pretend to be a tag itself. It is also capable of some less obviously useful operations that might come in handy for development work.”