How would this work, exactly? Usually stream parsing requires handler functions, which would imply passing functions at the commandline. I can't think of how you would do this with pipes.
I'm sure there are better ways to do it, though.
I'm sure some handlers could be generalized a bit (for example, scanning for regular expressions). But I don't think that the SAX/commandline solution is much better than the SAX/program solution.
Am I missing something?