Opinion on Notify Request Header

I am interested in the group's opinion on the Notify Request header
proposal in Section 6.  Do you think this is a good idea, or a bad idea?
Server implementors -- how difficult would such a mechanism be to

>6. Notify Request Header (proposal, for comment)
>Whenever the NotifyRequest header is included in an HTTP request, the
>server should send update information on the progress of a request.
>Notify_Request = "NotifyRequest" ":"
>It is common, in asynchronous environments, to provide a mechanism to
>describe the status of a request as it is processed. As we provide for
>more and more powerful methods, which have longer and longer processing
>times, might we not want a similar feature for HTTP?


- Jim