[nextstep]

I'm pretty sure the bottom billion still don't own cellphones. But this is a smart idea for the bottom billion of cellphone owners.

[mkr-hn]

It was 5 billion in 2010: http://reviews.cnet.com/8301-13970_7-10454065-78.html

Life for the average person in the bottom billion isn't great, but it's getting better.

edit: http://en.wikipedia.org/wiki/List_of_countries_by_number_of_...

[westbywest]

A cell phone can indeed be the one and only relatively high-tech possession for a poor family in an impoverish region. Used cell phones and/or low-end handsets subsidized by the carrier help them proliferate.

Vaguely tangential, a UCLA professor developed a microscope attachment for a cell phone camera, to permit remote phlebotomy and other telemedicine in areas lacking facilities otherwise. http://www.engineer.ucla.edu/newsroom/featured-news/archive/...

A good overview of this style of tech innovation is the Smithsonian Institute's "Design for the Other 90%." http://archive.cooperhewitt.org/other90/other90.cooperhewitt...