Comment Single-chip response (Score 1) 38
Hmm... provided you could build some capacitance into the die, it would be trivial to manufacture, en-masse, an array of incredibly inexpensive devices that could respond to a light-signal stimulus, much the same way that RFID tags respond to a suitable RF signal.
I can't think of an immediate application, but the key technical difference would be that you can transmit focussed, directional light in a laser, which is a much more difficult and wasteful feat with RF. You could therefore elicit a response from one of these chips at pinpoint accuracy and great range, which is not currently possible with RFID. I'm sure some more innovative people than I could conceive of a novel application.