Google Tone was recently added as a Chrome Extension and I think its pretty cool.
It uses a tone to transfer information (urls) from one computer to another using the microphone.
In the following video, I send a link using a tone to my desktop computer and send a link from my desktop computer to my Chromebook. On the receiver end, you receive a notification which you can choose to dismiss or open.
A big issue for GAFE is getting a group of students on a specific site or url. Attempts to solve this problem have included start pages, QR Codes, tiny urls, and even purchased domains. With this extension it can get "real simple", a teacher could go to a site and use the extension to send the url to every Chromebook in the class. Students could click the notification and begin getting to work.
I was concerned this could get spammy. Jonny could abuse his new found power and begin sending inappropriate links to the entire class. As +Ken Yeh mentioned two safe guards that will prevent this is you will receive a notification from Jonny and an audio sound. You can respond to it in a similar fashion as if Jonny blurted out in class.