While rumors have circulated in the past about Microsoft developing its own phone, the Wall Street Journal now claims that Ballmer and co are testing a new device in Asia.

According to "people familiar with the situation", Microsoft is working alongside component suppliers to test a new cell phone design. Details are, however, scant: one source told the Journal that the screen of the smartphone is "between four and five inches", and… that's it.

It's not surprising, given Microsoft's launch of Surface, that people are keen to speculate about the fact a cell phone could be hot on its heels. Plus, it would be kinda cool: Microsoft's eye for design is keener than ever, and while WinPho is great, it's yet to make the impressions it could. Or even should. A Microsoft phone could change that.

Still, it's important to not get too excited. As we explained last month, just because Microsoft is testing hardware doesn't mean it's going to launch a phone:

[E]ven if these reports turn out to be totally accurate - and that's far from certain - this does not mean that Microsoft is close to actually making a phone you can buy. It doesn't even mean it ever will. Just that it's developing the hardware, and testing it. That's it.

Where there's smoke, though, there's often fire: if rumors like this continue to pop up, it might not be long before you're holding a Microsoft-made rectangle to your face. [WSJ]

WSJ: Microsoft Is Testing Its Own Smartphone