In place of the pipe, you can use other commands (like nc, to send the video stream from another network device to the kindle video). Instead of zcat getting input from a file, it could get its input from nc, which gets it from another nc on the other side of a network, which gets its data from a file or a live streaming video source (or live continuous screencapture, like a super-simple VNC).
One such tool I wrote is a filter program that runs on my linux host PC and in the kindles, and converts raw video on STDIN to the .gmv format on STDOUT. It just needs 600x800 8-bit video piped to its input. To test it I need a better raw video source. Linux mencoder inserts extra AVI crap into its supposedly "raw" output format.
In linux, "filter programs" are programs that read data on STDIN and write modified data to STDOUT, and are normally used between pipe symbols "|".