Google Tone
chrome.google.com
chrome.google.com
Am I just missing something?
Imagine giving a presentation in a public conference, you can provide resource (per x slide) to all of your listeners(strangers and what not) for referencing without ever saying anything about it.
That being said, having a way to do this on the fly could be pretty convenient now that I think about it more.
Off the top of my head I can think of a few neat things I could do in a room or building full of devices set up to listen in this way. Not everything is a cynical plot. I've found that most things can be exploited for malicious (or just pranking/annoying) ends but it doesn't stop us from trying out new things.
Edit: just thought of another one I might try out - use tones in audio track to send browser to a page that changes the color of my Hue lamps. Probably not super useful in the current state but the concept is great and would let me make synced lighting tracks. I wonder how well this would work with less audible (or at least less distracting) tones in a similar application?