The Economist discusses a possible successor to what has become an everyday necessity.
"AMONG the many new gadgets unveiled at the recent Consumer Electronics Show in Las Vegas was a pair of smartphones able to exchange data using light. These phones, as yet only prototypes from Casio, a Japanese firm, transmit digital signals by varying the intensity of the light given off from their screens. The flickering is so slight that it is imperceptible to the human eye, but the camera on another phone can detect it at a distance of up to ten metres. In an age of Wi-Fi and Bluetooth, flashing lights might seem like going back to sending messages with an Aldis lamp. In fact, they are the beginning of a fast and cheap wireless-communication system that some have labelled Li-Fi."
http://www.economist.com/node/21543470