Geopoll is a survey firm that mostly focuses on the African continent. They offer simple surveys with pay. However, the money gained can only be withdrawn in form of airtime. You download their app from the play store, register and you are good to go.
Surveys range from personal questions to supermarket price checkers. They also have a slot for billboard photography. Here, you are required to take a good photo of specific billboards in major cities and that earns you 2 dollars. The price checkers are worth 2 dollars too but come once monthly. It is a good way to earn airtime.
However, I feel that they should have introduced payment systems like PayPal or Mpesa since not everyone would need airtime.