It's only recently, though, that experts have tried to quantify how these products have benefited the poor.

In their recent study "The long-run poverty and gender impacts of mobile money," Tavneet Suri and William Jack assess mobile money's contribution to poverty alleviation in Kenya, the country where the "mobile money revolution" began.

Complementary products like the interest-earning mobile banking service M-Shwari and retail payment platform Lipa na M-PESA have only added to its popularity.

From surveys they conducted between 2008 and 2014, Suri and Jack find that M-PESA has lifted 194,000 Kenyan households—about 2 percent of them—out of poverty. It has done so, they conclude, mainly by making it easier for the poor to protect themselves against negative shocks to their wealth and income stemming from events such as bad harvests and general economic downturns. This enables poor citizens to enjoy a more stable and predictable flow of income and therefore have a smoother pattern of spending over time.