UPDATED Microsoft is currently testing a Slingbox-like add-on that would allow Windows Media Center users to watch programming on their PCs from anywhere using mobile devices and laptops, BetaNews has learned.

The feature uses a software application rather than a set-top box, as Slingbox utilizes to control a TiVo, cable or satellite box remotely. The resulting stream would play through Windows Media Player.

A demo viewed by BetaNews last week indicates that the service would even work over slower mobile data connections, such as EDGE.

Unlike Slingbox, only existing content could be viewed, as there currently is no way to control the Media Center PC remotely. However, one could start recording a live broadcast, and would subsequently be able to view it through the stream.

The recorded programming would appear through a Web interface that would then launch Windows Media Player to play the stream, the demo indicated. The bitrate of the video adjusts automatically based on the bandwidth available.

Joe Wilcox, senior analyst at Jupiter Research, says the streaming feature is a logical step. "Microsoft already has extended Media Center capabilities, for example, with the remote programming of content to record. Streaming content is another natural extension of Media Center capabilities."

Trials are now underway internally with plans to eventually publicly test the product. However, sources say Microsoft is wary of copyright issues that surround devices like the Slingbox, and is attempting to ensure that such a product would not draw the ire of broadcasters and copyright holders. Slingbox has become quite popular in recent months following its release last year. Since the company is privately held, it does not release sales numbers, but high-profile users like Robert Scoble have helped the device attain a cult following.

Requests for comment from Microsoft were unanswered as of press time.