>More of the problem is that it doesn't work room to room, only line of sight like with a remote control.

If you could cheaply make the lights transmit and receive, and if the data were recoverable at very low illumination, you could employ mesh routing -- there's often quite a bit of overlap from lightbulb to lightbulb.

But you're correct -- answering the LoS problem is significant. This could be very useful in many applications, but it's no silver bullet.