I have written several times on the benefits and struggles of digital signage and RFID. I picked this information up from Slashdot. A new technology allows measurement of the RFID field surrounding the RFID reader. The video, created by Timo Arnall and Jack Schulze, explains well how the technology operates.

"This image is a photographic mapping of the readable volume of a radio field from an RFID reader. The black component in the image is an RFID reader... The camera has been fixed in its position and the reader photographed. Using a tag connected to an LED we paint in the edges of the readable volume with a long exposure and animate them to show the form."

With over 4 billion RFID tags in the world, it is certain that this technology will continue to inundate our world. Any technology that allows us to understand how things work more clearly is significant, especially with something as far reaching as RFID. When RFID tags outnumber people, this stuff will be immensely important--especially if it's embedded in your brain. In that case you'll certainly wish to see how far the field reaches :)