On reflecting over the discussions surrounding the proposed PSR for HTTP middleware (on which I am coordinator), I realized there's no reason there should *not* be a "request-only" PSR-7 middleware dispatcher.
So, here is Telegraph to fill that void.
Built over this past weekend, Telegraph is essentially a copy of Relay, which is a "request+response" middleware dispatcher. (There are a couple of minor differences.)
I also took the time to port the existing Relay middleware over to Telegraph. You can find the Telegraph middleware here.
I was asked over the weekend, "Is this a sign that the HTTP middleware proposal is moving from request+response to request-only?" (/me shrugs) I just figure if there's such a need for something like that, perhaps it should be made available.
Oh, and I was able to quality-check and release it using Producer.