Microsoft said on Tuesday it is developing a slimmed down instant messaging client that will run on Windows Mobile-based cell phones and portable devices to extend the capabilities of Live Communication Server 2005 to business users on the go.

The new mobile messenger application is based on the user interface of Microsoft's forthcoming Office Communicator 2005. Communicator, formerly code-named Istanbul, integrates IM, voice, video, telephony and Web conferencing capabilities into a single interface and makes them accessible in Microsoft's Office applications.

Microsoft's Windows Mobile client will offer secure instant messaging and presence sharing across all types of wireless networks, real-time access to business contacts, and a familiar Windows interface.

"Information workers spend a lot of time away from their desks for meetings, travel, customer visits and other demands, and having mobile access to enterprise-grade real-time communications can help them work smarter and more efficiently," said Gurdeep Pall, corporate vice president of Microsoft's the Real-Time Collaboration Group.

A beta release of the Windows Mobile client is slated for the second half of 2005. Microsoft also announced that mobile handset maker Research In Motion (RIM) will develop a Live Communications Server Client for its BlackBerry line of devices, with a trial slated for September.

"Through the new Windows Mobile client and innovative mobile solutions from a vibrant ecosystem of developer partners, we'll offer mobile users an integrated communications and presence-sharing experience, all within a security-enhanced, trusted environment," added Pall.