Remote controlling a Windows Media Center from a Windows Phone isn't anything new at all - with the launch of Windows Vista, Microsoft introduced Windows SideShow (which never found an audience at all) and later published a Windows SideShow Beta for Windows Phone which allowed users to remote control some functions of the Windows Media Center. And now, since Windows Media Center is pretty much a standard for most Windows 7 versions, remote controlling a Media Center might make even more sense, The Land Dolphin is currently working on an application called "Meteor" which allows to remote controlling Windows 7 Media Center straight from Windows Phone 7.
Meteor is an application that runs on Windows Phone 7 device that, when coupled with a small service on Windows Media Center PCs, allows to remotely access and play all kind of music albums, TV shows and movies on a Windows Phone 7 integrated "Metro" experience. It's personal and it's relevant.
There's no release date given yet but since Windows Phone 7 is yet not released, it doesn't matter. Nevertheless, we can only hope that Meteor will make it to the market since I'm a big fan of Windows Media Center and connected and converged services and applications like Meteor make smartphones even more useful and smarter.
Cheers ~ Arne