The country that I would identify that fits these criteria is Botswana. Botswana has generally (though not on all measures) done much better than its neighbors in Sub-Saharan Africa.
For example, the country's gross domestic product per capita (when adjusted for purchasing power) is $16,300. This is extremely high for Sub-Saharan Africa, where countries tend to have incomes less than one tenth of that with the lowest (Democratic Republic of the Congo) haviing a mere $300 per person.
As another example, Botswana has a relatively low rate of maternal mortality, with 190 maternal deaths per 100,000 live births. This is horrible compared to the 24 deaths in the United States, but it is very good compared to the figure of 990 in Guinea-Bissau or the 970 for Burundi.