Microsoft might very well be gearing up to launch a Google Chromecast rival. While the tech giant hasn't announced anything official yet, one of its latest FCC filings details a device codenamed HD-10, which features WiFi, HDMI support and a USB connection. Those three will sound familiar if you know what the Chromecast is, but what really demystifies the device's nature is a separate document on the WiFi Alliance website. That filing, unearthed by Nokia Power User, called the HD-10 a "Miracast Dongle." Miracast, as you might know, is Microsoft's screen-sharing technology available on Windows 8.1, Windows RT and, most recently, Windows Phone 8.1, though it's also built into Android 4.2 (and later) and BlackBerry 10.2.1.

The dongle will likely be able to mirror phone, tablet and laptop screens on a TV then, so long as they're loaded with those platforms. Unlike Chromecast's technology, though, Miracast can only show what's on the source device's screen à la Mac OS X's Airplay Mirroring, meaning you can't play mobile games while you're casting a show on TV. That's pretty much what's known about the mysterious casting stick for now, but we might hear more about it (and find out if it's priced as aggressively as Chromecast) soon enough.