LiFi→

ScienceAlert:

The benefits of Li-Fi over Wi-Fi, other than potentially much faster speeds, is that because light cannot pass through walls, it makes it a whole lot more secure, and as Anthony Cuthbertson points out at IBTimes UK, this also means there’s less interference between devices.

Still not the peak of security, though- that would be tight beam laser communication. Similar concept, in that you’re transmitting data via what may well be visible light, but it takes advantage of the coherent (and very aimable) nature of a laser beam to ensure that only the person you’re trying to talk to gets your message.