New in Windows Phone 8.1 (as modelled in the Preview edition) is a feature called 'Project My Screen' and hopefully its function will be obvious from the name. It's rather limited (you have to be plugged in via USB) and does require special server software on a desktop or laptop though - with the Windows PC version now being available here.

Of this new download for Project My Screen, WMPU notes:

Unfortunately the app is a Windows desktop app, not Windows Metro, but is still full screen on the desktop, making meaning you can not snap the app to the side of your screen or open it in a window and still get other work done.

Update: Alt+Enter will return the app to windowed mode on the desktop, which has just made the app 1000% more useful.

To get started, install the 'Project My Screen' app, activate Project My Screen in Settings on the phone, and connect your phone and run the app on your desktop.

The whole 'Project My Screen' thing is clearly aimed at a future where devices support full wireless streaming to the likes of Miracast and Chromecast servers, but it's not clear whether many current devices will actually support these, even with future OS updates (the Lumia 1520, 1020 and a few others are rumoured to be hardware compatible - maybe there's a RAM/resource requirement?).

In the meantime, this implementation seems aimed more at developers and enthusiasts than consumers.