I think that's exactly what Backlift does: https://www.backlift.com/

(I'm not affiliated with them)

There is some stuff that we want to handle differently, like when you increment a field it is usable locally but maps to an increment operation rather than a set on the server. So for a slew of details like this, overriding Backbone.sync wasn't quite sufficient. I hear the concerns about the trickiness of using plain Backbone with Parse, though - that is a design issue we are thinking hard about.