Project Loon, from Google:
We believe that it might actually be possible to build a ring of balloons, flying around the globe on the stratospheric winds, that provides Internet access to the earth below. It’s very early days, but we’ve built a system that uses balloons, carried by the wind at altitudes twice as high as commercial planes, to beam Internet access to the ground at speeds similar to today’s 3G networks or faster. As a result, we hope balloons could become an option for connecting rural, remote, and underserved areas, and for helping with communications after natural disasters.
Google testing out this system now in New Zealand. If they can get it to work they plan to use ballons to provide wireless internet access to hundreds of millions, or even billions, of people that don’t have access now. These ballons would float about 20 km above earth in the stratosphere (so well above where commercial airline traffic) and they are really working somewhat like to satellites.
Though ballons are much cheaper to put in place than satellites they also offer significant problems as they get blow around by wind (which is why they haven’t been used before and why Google is going to experiment to see if they can get it to work). The ballons will use solar power and be controlled by a mission control to move into different wind zones to position themselves.