I usually don’t refer to any non-ham companies here on my site but because this is also about communications and the technique used seemed so amazing to me that I do have to mention this here.
A few weeks ago I was invited to the DIY-shop of one of my colleagues for a demonstration of his new computer system and, connected to it, the new shelf labeling system.
At first I could hardly believe it but their labels are updated by modulating the light of their (existing) fluorescent lights! So no need to install any infrared transmitters or to pollute our RF-spectrum with another radio signal! More info can be found at: http://www.ilid.com.au/
(Just to be clear I am in no way affiliated to Ilid! But if they offered me a rountrip plane ticket to go and visit their premises I wouldn’t refuse it [hint][hint])