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.“