
The best way of explaining it is that AppleTV let's you do this with an iPhone/iPad:
Using an app like AirServer, you can also point it at your laptop instead of AppleTV.
Imagine how much better the end-user experience of someone attending a web conference, conference room presentation, or even an auditorium can see your demo when it's exactly the user experience that a real iPhone and iPad application have instead of an approximation of it.
Here's a quick recording of what it's like. Fast forward to 1 minute 30 seconds if you just want to see the punchline.
A few notes, make sure you note the "double-click" and swipe left twice to get the AirPlay menu on your iOS device. I did not even know that menu was there previously.
Also note that some wireless networks may block the video projection. I could not get the display mirroring to function on the wireless network at work. I've heard that using an Ad-Hoc network or a Hotspot network should work in situations like that, so I'll need to play with that still. If you have trouble using it at first, make sure you're not on a wireless network that might be locked down.
Now go build an amazing mobile application on Cloud Foundry that I can demo!
Update: The Ad-Hoc network setup is super simple, I recorded that too. Just create a new Ad-Hoc network on you machine, connect to that network with your phone (no IP setup needed) and you're good to go.