event photography - How can I get barcode-scan information into my photo metadata, onsite, untethered?

I need a DSLR camera with a barcode scanner for on-site tours photography, which means it needs to be untethered! The image would have to contain the barcode scanned information in the image metadata or in the name itself.

I've seen solutions like, Foolography and a $2600 Canon Studio Edition launched in 2010. But I'm not sure of either those products!

So I'm asking the gurus here how I can get this working, which camera would I need and any accessory necessary?

I'm trying to recreate something like I saw the on-site volume photographers do in Disney's parks.