Beeping is a known phenomenon in Africa. A beep is done by calling and hanging up after one ring. This is a cheap alternative to sending a text message or calling someone.
Daniel Peltz built a simple live feed installation, that allowed Cameroonians to "beep god". A spontaneous public debate occurred around the site of the projection, which lead to several interviews. Watch the video of the installation and the interviews.
The first interviewee made some examples, how different beeps can have different meanings, depending on the context:
The beeping function was created as a means of getting someone to call you back. When I beep someone in Europe, it means "call me back," usually urgently.
But here in Cameroon, what does the beep mean? If I beep you once, it might be to say hello. If I haven't seen you in a while, it could be to say I haven't forgotten about you, I'm thinking of you. It could be to remind you that you should bring me the book you promised. If you take me to the bus in Yaounde and I beep you later, it would mean I've arrived safely. Or, if we're separated and I beep, it could be to say that I've gone back to my house. We've developed a whole system of coded, culturally specific communication.
This corresponds to the statements of Jonathan Donner in his paper "The Rules of Beeping", that the meaning of a beep depends on the context.
The second interviewee states the hypothesis, that Cameroonians (could apply also to other African countries) developed this kind of communication because of their tradition to use drums for communication:
If Cameroonians have expanded the meaning of a beep it is due primarily to their cultural heritage. They have a tradition of communicating through sonic resonance when they used tam-tams for example.