I've been reading through the .pdf you linked to, and it's very interesting indeed. I probably could live with a range of 3m or so, so I could go for a passive RDIF. I've looked at Farnell and their supply of RDIF components, and it's quite hard for me to determine what I'm looking for, seing I've only heard about RDIF briefly in the newspaper.
Could you point me in the direction of a low cost, passive RDIF kit? I only need the reader to turn on a loudspeaker with when the tag is in range, and the reader should be able to be supplied from the grid with 230v.