BlackBerry maker Research in Motion (RIM) has released an update for its wildly popular BlackBerry Messenger (BBM) service. The update allows users to make voice calls to other BBM users if both are connected to a Wi-Fi network.

The latest version of the Canadian company’s messaging platform, BBM 7, began appearing in the BlackBerry App World on Tuesday.

BBM has come under threat in recent years from cross-platform services like WhatsApp and Viber and has seen dwindling popularity in developed markets, including the US and Europe. BlackBerry and BBM remain extremely popular in emerging markets, however, with BlackBerry devices continuing to sell well in South Africa because of low fixed monthly costs for BBM and on-device e-mail and Web browsing. BBM is particularly popular in the youth market in South Africa and other emerging markets, including Mexico, Nigeria and Indonesia.

The new voice feature does not work over cellular connections and requires both the user placing the call and the user receiving the call be connected to Wi-Fi. This limitation may reduce uptake of the service given that many BBM users in emerging markets may not have regular access to Wi-Fi networks.

“BBM began as a convenient and effective business messaging tool and today it’s an essential part of daily communications for customers around the world,” says TA McCann, vice-president of BBM and social communities at RIM.

“Now, with BBM version 7, customers have a new option: they can text and talk with their BBM contacts, near and far, for free.

With the new BBM, users can also make use of a split-screen feature so that they can reply to other text messages while on a BBM call, or even use other applications. BBM 7 is available for all BlackBerry smartphones running the BlackBerry 6 operating system or higher.