there is a video of Raspberry PI with airplay support.
since the device is arm powered and running linux,
it should be possible to implement for our TV`s.
there developer descripes it in the comments
Next thing,A small AirPlay service runs in the background and announces itself (using Bonjour) as an Apple TV2.
This means when playing a video on an iOS device, an Airplay menu option becomes available to send the video to that device.
The R-Pi does a little communication with the iOS device and gets an http URL to play. This may point to the iOS device or the internet.
The media player on R-Pi plays the video from that URL.
XBMC has now native airplay support too, maybe someone could find a way to port it?