I this part of the world – Kenya. WhatsApp is a very popular messaging app for those with smartphones. A whole lot of people still rely on text-messaging though.
In my case, I use WhatsApp & Text (though rarely) when on mobile. And Google Talk during the day when I’m at work.
I imagine a lot of people do this too only if it’s not Gtalk, it would be Yahoo Messenger or Skype Chat.