I got this idea years ago, somewhere in 2004 after I had heard both of RFID and E-Ink. The order is irrelevant ;) The idea is simple, we take:
1) RFID readers, which send radio waves to tags, which pick up some of the energy in the wave, do some computations and send a reply. The tags are brilliant: no batteries, no connected power source of any kind except for the antenna.
2) E-Ink displays, which need power only to change pixels. After the power is cut off, the pixels remain in their current state.
The result: a small tag with a display. The display gets initialised and updated by an RFID-reader and after that retains its state indefinitely.
Perfect for price tags on shelves in supermarkets, which need to be updated every now and then but are hellish to replace.
I soon found out in 2004 that Epson had already done this: http://gizmodo.com/026090/epsons-electronic-ink-%252B-rfid--21st-century-price-tags