I'm surprised no one has made this available in consumer product form, but I guess it would require RF sources to know what the responding signature meant in identification (like a national DB).
You can get scanners yourself that can read standard RFID tags, they're just kind of pricey. Also, unless you know what the tag means, all you get is some random numbers (sort of like a UPC code). It's probably just linked to a record in a database somewhere (that you don't have access to).
A few publicly available things that already use them:
Mobil Speedpass (seen similar things recently from credit card companies).
EZPass/FastLane (NE/Mid-Atlantic tollbooths; no more stopping to pay tolls).
McDonalds has been running trials with it (actually using the Speedpass tags in those states) so you don't have to hand them money at the drive-though.
Some big chain stores (Wal-Mart, etc.) are starting to use them for inventory control on their shipping crates/pallets.
Orwellian fears about using RFID to hunt people down are a little out there, IMO. It's not like you can pick these things up from miles away.