This is pretty amazing:
Treadle pumps were first introduced into Bangladesh in the early eighties and, since then, over a million have been sold there. They are now making their mark in Africa. Countries such as Kenya, Zambia, Zimbabwe and Niger have adopted the idea, changed the design slightly to suit local conditions and begun marketing the pump with great success. The pumps cost between $ 50 and $ 120 depending on the country. (source)
The treadle pump is cost effective; it cost US$ 20 in Bangladesh and generates US$ 100 or more per year. Together, these pumps add over US$ 100 million every year to the GNP of Bangladesh. Production and sales are now sustainable without any external aid. The treadle pump for irrigation was developed in the late 1970’s in Bangladesh. After wide-scale promotion by IDE they are now being produced in 300 local workshops and used by more than one million poor rural families that otherwise could not have afforded an irrigation pump. (source)
Its pioneer IDE has also other interesting tools like arsenic filter, low cost water storage etc.