Dimagi
Dimagi's mission is to use technology to improve the lives of people living in underserved communities everywhere, especially through the use of mobile technology to strengthen programs in many sectors. Dimagi works in over 30 countries, mostly in the Indian subcontinent, Africa. The main product CommCare (http://www.commcarehq.org), allows for NGOs to write and maintain their own mobile applications without programming knowledge, and Dimagi also offers extensive consulting services with our partners as they start to introduce mobile software into their program. CommCare applications are geared toward usage by illiterate and low-literate users in sectors such as community health, clinical settings, agriculture, small business, infectious disease, maternal and child health, counselling for people in stigmatized and vulnerable professions, and can be used for many others; and the underlying software is repeatedly field-tested for usability in these settings. And it is awesome.
Dimagi has strong field teams around the world, with offices in Boston, Delhi, Cape Town, abd Senegal. All of Dimagi's core software developers also routinely spend weeks at a time at at project sites and shadowing a field manager, usually about twice a year per person. In my opinion, Dimagi is the most mature, on-the-ground, and innovative company of its type, but, hey I just work here.