I had an email exchange with Sean Reid maybe two years ago where I described to him a design like this one. My proposed design had a 2nd (tiny, P&S) sensor in the place of an RF window driving the EVF so it could be implement a real "ERF". This is not as nice as what I had imagined, but it's _very_ nice still. I love the idea of more detailed information being placed in an RF viewfinder.
They could sell a hundred times more of these if they had given it an interchangeable lens mount.