[kaoD]

It seems to me that this isn't feasible in pure client side because the server would have to agree on some kind of protocol.

Server-side is mandatory here. Unfortunately I cannot recommend any since I don't do Ruby :(

Maybe you don't need a framework but just a JSON-RPC[1] library.

[1] http://en.wikipedia.org/wiki/JSON-RPC

[robotmay]

I'm really just looking for a model system that allows simple updates of objects in its identity map with data from an arbitrary source. Backbone is the closest I've found to supporting this with the least effort. I'd rather like to use Server Sent Events, as there's decent support in a variety of languages and it's pretty simple; it's just that no current frameworks seem to have been built with those sorts of technologies in mind.

I've largely resigned myself to having to hack support into anything I try.