Ah, well... either way you wouldn't be getting anything but the uncompressed live view image which is far, far from hd. Sounds like you need a video camera.
Of course if the movie mode video quality of your camera is sufficient, one could probably experiment with streaming the video file that's being saved to an SD card. But keep in mind that SD card write speed is already close to being maxed out with video, so reading simultaneously might not work satisfactorily at all.
