Android/iOS/Windows Phone: Today, WhatsApp announced that video calling is coming to its various apps over the course of the next few days.
WhatsApp already includes voice and text, so video's the obvious next choice. It should work exactly like Skype, FaceTime, Hangouts and the variety of other options out there. There's no exact time or date on when the video calling update will roll out, but it should arrive in the app "in the coming days".
WhatsApp Video Calling [WhatsApp]