You're right. I'm looking into HF RFID reader module, but haven't gotten a response back from the vendor. (had to contact for pricing) Runs at 13.56MHz. The only issue I see is that the tags are a mostly the paper ones like the ones you get in books from the book store. I have been reading about external antenna options that might address the range issue. If that will work I just need to worry about collision control (reading multiple tags simultaneously)
This seemed a lot easier before I got into it. It's still a fun exercise. Maybe I'll just build a robot.... 
Dale