The single biggest reason that the appropriate technology movement died and most technologies for developing countries never reach scale is that nobody seems to know how to design for the market.

Paul Polak has brought 19+ million farmers out of poverty. His work is dedicated to designing products for the Other 90% (the 2.6 billion customers who live on less than $2/day).

http://unreasonable.is/how-to-design-for-the-poor/