I was just looking at the small versions of these on shelves in Eurospar the other day. The price of an offer was missing and I asked an assistant to do a price check. He said there was a problem sending the price to the device. I hadn't realised they were screens until then, although I was aware of the technology of intelligent price display labels. Presumably the display is similar to the E-ink types used on a Kindle, not needing a backlight and visible in bright ambient lighting conditions. I thought they were just pieces of card.
