They’ll have to carry the wireless devices as a way for border guards to access the electronic information stored inside a document about the size of a large index card.Link (Thanks, Anne!)
Visitors to the U.S. will get the card the first time they cross the border and will be required the carry the document on subsequent crossings to and from the States.
Border guards will be able to access the information electronically from 12 metres away to enable those carrying the devices to be processed more quickly.
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.