There are actually larger digital imaging sensors than medium format, for instance, see this link from dalsa
which is a 100 MP 4inX4in sensor.
As for large format photography, check out some of the Ultra Large format camera's out there (e.g. Wisner cameras), these can be as large as 20 by 24 inches sheets of film. Polaroid actually has a 20x24in "instant" camera, its quite large, and supposedly there's also a Polaroid 70 in camera.
Gordon Laing wrote:
The other thing about large format is it's one shot at a time - no roll of film.
Caleb, you'll have seen them before - they usually have sheets which the photographer gets under when composing -think Ansel Adams. The bigger cameras used plates up to 10x8in.
And yep, they are still used for some reconassiance - anyone see that episode of the BBC's Coast where they showed how the Ordnance Survey (UK mapping co) operates? I'm sure that was large format photography...
Not sure if there's an large format digital though as the sensor would cost a fortune and be almost impossible to manufacture. In fact medium format film covers formats up to 6x9cm and we're nowhere near that with digital yet.
So the interesting thing about some of the medium format systems with film or digital backs is the digital one normally has a sensor that's smaller than the film - so there's a crop factor again!