Wave is really good! (I use it) Another thing one can do is to work for some mobile money company in a developing country to design products that benefit the poor (e.g. saving, credit, that I mention in the other post), like the American guys I met in Myanmar’s Wave Money (but they are still early stage and has many challenges before having an impact). (Not suggesting you should do it though—involves moving to a developing country etc., and could be much less likely to succeed due to regulations etc.). BTW this is the mobile credit scoring company I had in mind: http://tala.co/.