The good news
WhatsApp voice calling is now available for android users and the App is updated so you can make calls with your phones without getting tweaks or invites from friends. This process was not openly available to everyone, but has been reviewed; android users can now enjoy WhatsApp new wonderful features.
The release announcement
The feature was released about a month ago after which was initially available to few users, the calling feature was then made available to more users but using it was only made possible by receiving an invite or call from a user who had the feature activated on their phones. The snag now is accessing the latest version of this App new feature from Google play store as the version there is much older.
How to get the latest version
To get the updated version you will need to install and download the APK installation file which is the latest Whatsapp version (2.12.19) from the website of Whatsapp.
This new feature from WhatsApp will provide stiff competition for other apps like Wechat and Skype that provide similar services of making voice calls.
The feature is yet to be made compatible to the users of iPhone, BlackBerry and Windows phone handsets and such users will be eagerly expecting the feature.
WhatsApp has not yet properly introduced the feature to the market and is not yet sure if this is a feature set to stay for the long haul or it is just for a limited time.