[kelleyk]

This is neat, but not new; check out Talking Lights, for example (http://www.talking-lights.com/) --- they were an MIT professor's startup and went out of business a few years ago.

There are also some cool indoor location-finding applications, from what I recall; if each fixture emits a unique ID and you know how they are laid out, you can figure out where in the facility you are fairly easily.