The folks over at Android World have delivered some hard evidence in the form of screenshots of WhatsApp's voice calling interface, along with evidence hidden in the latest app builds.
According to Android World, the latest version of WhatsApp put out on the company's website contains evidence of a network screen that logs how much data has been consumed by calling via WhatsApp. They've also put up a load of screenshots that give us a fair idea of what the interface will look like.
Another indication that WhatsApp's voice calling feature is coming soon is the app seeking for permission to turn on a device's Bluetooth. This has to do with the call feature allowing users to use Bluetooth headsets when in a call – a fairly rudimentary function.
The report notes that the voice calling feature is somewhat separated from the chat section, but it's hard to judge whether it will remain that way once the feature goes live. A feature for listening back to calls made on WhatsApp may also be included, but calling will be pretty similar to how users start an IM conversation.
The call logs will be displayed on the same screen which currently shows contact information and media files received from them. However, for now there seems to be a dedicated call log screen, probably to stop the contacts screen from getting too clogged.
There's no indication on when the voice calling feature will be launched, but looking at the development so far, we expect that to happen sometime early next year. The other big news is the development of a WhatsApp web client, that will bring the service up to steam with some of its rivals.