Few weeks ago I reported on a Nikon patent about a light meter built into the prism. Nikon has filed a series of related patents. One of them is 7876373 which describes a camera with a hybrid viewfinder:
"One of the objects of the present invention is to provide a means capable of confirming the state of field and the photographing area of an image pickup section in a camera capable of observing an electronic image through an optical viewfinder.
Moreover, one of the objects of the present invention is, in a camera capable of observing an electronic image through an optical viewfinder, to provide a means capable of acquiring various kinds of information depending on the situation without detaching eyes from the viewfinder."
Next patent drawing shows zooming for only a portion of the viewfinder:
Another drawing shows a build-in flash with an additional lens that can capture the surrounding environment and display it in the viewfinder:
The above described hybrid viewfinder will probably be implemented with two different sensors and patent application 20110038623 explains in more details the purpose of those sensors:
"A camera includes: a first sensor of a storage type that has a plurality of pixels; a focus detection unit that detects a focus adjustment state of a photographic optical system based upon a detection signal from the first sensor for a photographic subject; a second sensor that acquires an image of the photographic subject; an extraction unit that extracts a main photographic subject region from image information acquired by the second sensor; and a control unit that controls accumulation of electrical charge by the first sensor, based upon values outputted from pixels of the first sensor that correspond to the main photographic subject region."