SSE is not extremely HTTP-y but it at the core is the sort of thing we have used for ages for the same thing we use web sockets. The only difference between SSE and old good polling is the presence of a nice API on the browser side.

We have worked with SSE, HTTP/2 and HTTP/2 Push of SSE event streams and it is a combination made in heaven. In particular, we use SSE events to have the server announce to the browser when a particular segment of an interlaced or progressive image has been delivered. With this combo, the SSE events can be delivered on the wire very close to the data frames for the image pieces themselves.