Philips has acquired Luciom, a French startup that makes Li-Fi products, which allow for very fast network connections over short distances by flickering an LED at speeds that are too fast to register on the human eye, and which can ever work in the dark by operating at low dimness settings the human eye perceives as "off."
Li-Fi has been knocking around since 2014, and almost everything written about it online is barely reformatted press releases and breathless boosterism videos like the one above. The Wikipedia article on it is well-sourced, though, and has been purged of most of the stuff that reads like an advertisement.
The basic premise is that your lightbulbs have access to a lot of unregulated electromagnetic spectrum — light! — that radio-based networking systems lack. There are some shortcomings to using freespace light for networking, especially the range — leave the room and close the door, and your network link drops. Li-Fi marketers spin this as a security feature (your internet signal is private within a single room), but they don't really think this through: with Li-Fi, your threat model needs to include light escaping through windows, the cracks under your door, and so on.
Li-Fi nodes use LED flickers at intensities and speeds that are imperceptible to the median human eye (I'll wager cash that someone out there will claim to be have six-sigma flicker-detectors in their eyeballs that trigger terrible migraines and worse in the presence of Li-Fi modulators). Then they sense this light with small, cheap sensors — these sensors don't necessarily need to have line-of-sight to the emitter, they can sense its flicker by watching the shadows.
The light spectrum available to LEDs is truly vast, which offers some possibility for keeping competing wireless signals from clobbering one another — one device gets blue flickers, another gets red, etc — and given that you get to recycle the spectrum in every room, it would take a bogglingly vast constellation of IoT devices or other networked gizmos to use it all up.
So: it's interesting, but it's not real, yet. Hilariously, the Li-Fi people have repeated the original sin of the wifi people and asserted that Li-Fi stands for the nonsensical phrase "Light Fidelity," a blunder that triggered years of pointless debate when the Wi-Fi Alliance tried it. The Li-Fi people have even inserted a doomed, superfluous hyphen! Everything old is new again, truly.
(via Beyond the Beyond)