Li-Fi

That's neat. I think it would be more of a 1-way broadcast type situation. Like if you're in a stadium and you want to broadcast an audio stream to everyone on their smart phones or something. It wouldn't really work in a wi-fi like situation where multiple devices are continuously uploading and downloading because even if there was a way for the phone to respond using the flash LED, I don't see how the receiver could really respond to multiple devices at the same time without complex hand shaking. I could imagine things like this for like a large lecture where everyone could just hold up their phone and receive the presentation slides without having them all connecting to the wifi and overwhelming the router, or in a stadium they could broadcast replays and/or the local radio station play by play over it, you could send emergency information over street lights or some sort of kiosk, put train schedules/announcements out on the lights in the cars, or maybe you could even use it to watch CNN or something on your phone/tablet while commuting, etc.