Provided are, among other things, systems, methods and techniques for light-based communication. One representative embodiment includes: messaging units disposed at different locations within a space, each including at least one light source (e.g., light-emitting diode or LED); at least one messaging/modulation controller coupled to the light sources and configured to turn the light sources on and off so as to broadcast input digital messages; a central server coupled to the messaging/modulation controller(s) and configured to selectively provide messages to the messaging/modulation controller(s) for broadcast by different messaging units; and an associate device coupled to the central server and configured to: (a) display a user interface for manually inputting information about individuals within the space and (b) provide such information to the central server, where the central server selects messages to be broadcast by the messaging units based on the information received from the associate device.