Paul Polak is a physiatrist by training but has spent the past 25 years working to alleviate poverty in the developing world. His non-profit, International Development Enterprises, has come up with innovative low cost technologies that have improved the local livelihood of people at the bottom of the pyramid. For example the simply designed bamboo treadle pump has sold over 1.7 million copies and generated over $1.4 billion in farmer revenue in Bangladesh.
Paul has encapsulated his learnings in a book Out of Poverty that describes a number of these technologies. More recently, Paul has posted an interesting video on You tube that summarizes his Twelve Steps to Practical Problem Solving.
Some of the observations are commonsense ones but it is remarkable how often people forget them in their eagerness to push technology.