Don't know about Kenya but used it in SA while on a visit and it works quite well. I was actually using it as my primary means of transport. I talked to an Uber cabbie on how it works; drivers actually get's a pin dropped at where you are when you "call" for the cab then they reply,(don't know what criteria is used to show you a cab has been found, it will be with you in x minutes, shows you the make and model of the car etc) you confirm, he or she comes, picks you up, drops you where you are going and shows you the cost (which is a mix of time taken and distance - calculated by Uber as the car moves), and you pay from your google play wallet, Paypal, credit card etc. Made jumping from place to place very easy.