And your cell phone knows. It automatically switches to vibrate, based on google maps information for your cell phone’s gps coordinates. Or you’re at work – you initially tell your cell phone where “work” is — and it does the same for a 50m radius. Just imagine what a useful feature this could be for students hurrying to and fro from classes — they wouldn’t need to keep changing the phone’s volume. Of course, cell phones that broadcast their gps coordinates may put their users’ privacy at risk.