We just came across a neat little iOS app called AirView which, as you can probably tell from the name, transforms your iOS devices into AirPlay
video receivers. And since iOS can also output video via AirPlay, this means you can use AirView to either grab AirPlay streams from your computer's iTunes, or you can stream videos from one iOS device to another (provided that they are both running iOS 4.2 and above, of course). Theoretically, little work is required to get the ball rolling -- just launch the app, then play your desired video clip from the source, and finally pick your client device using the AirPlay button.
We say theoretically, because it took us awhile to figure out that none
of our purchased videos worked, even though AirPlay supports DRM content -- the assumption is that AirView lacks the component for receiving authorization key. Alas, we stuck with our, ahem, homemade videos which actually worked very well over both iTunes-to-iOS and iOS-to-iOS connections, although sometimes we had to relaunch AirView and the iPod app to start a new stream. Perhaps some folks will have better luck than us, so feel free to give this app a go -- it is free, after all. Video demo after the break.