Nikon has been making waves with the announcement of their Coolpix S1000pj; a new digital still camera with a built in projector. Imagine... you take some digi snaps, and instead of crowding around a tiny little screen to share the fun, you can project those images on the nearest wall/t-shirt/bone china. It's a logical progression in digital camera tech. You can only cram so many megapixels into your pocket, so manufacturers piled on extras like facial recognition, printers, even GPS.
A convertible camera/projector is a fine idea - so fine that it's been done before. In 1957, famous jeweler Wittnauer introduced the Cine-Twin. It was an 8mm camera that bolted onto a special base to become a projector. The idea wasn't new in '57 either. In 1895 French inventors Louis and August Lumiere patented the "Cinematographe" combination movie camera & projector.
Developed by John Oxberry (Oxberry gained industry wide fame by developing a special animation camera stand that is still used by some animators today), the camera-projector combination was remarkably clever. Unfortunately that innovation comes at a price. The Cine-Twin was terribly expensive in its day, and was sold exclusively in jewelry stores. The exclusivity and novelty of the Cine-Twin outpaced any practical desire for such a device. Needless to say that neither this specific camera, nor the fusion of projector & camera made much of a mark in the decades since.
The camera was quite large for an 8mm model, even for the late 50's. It took a monstrous three D cells. The shooter was freed from winding the clockwork motor every few moments, but it did add dramatically to the overall weight. Adding to the fragility is that the delicate projector bulb of course rode shotgun inside the camera. Obviously you never want to knock any sort of camera around, but one with an expensive glass bulb inside?
The Cine-Twin is emblematic of the difficulties of convergence. Frequently the combo device doesn't offer the advantages of the separate original devices. One positive I can see is that in projector mode the unit is smaller than many stand-alone projectors, but would lack the throw or brightness of a larger dedicated unit. Perhaps there was an amateur filmmaker who benefited from having a compact way to shoot and share movies, but it came at a very high price.
The Nikon Coolpix S1000pj camera/projector combination is certainly a breakthrough in convergence devices (I hope that it can project motion video too). Unusually, I don't see the down side in this particular digital alliance. It looks to me like the Coolpix will be able to deliver the fun that the Cine-Twin just couldn't. While the idea of combining these two types of devices is well over 100 years old, sometimes it just takes a while to get the details right.
YouTube video demonstrating the Cine-Twin
Alan Kattelle's superlative book on home movies, including cameras
related:
Marvelously minuscule Minolta Mini-35 slide projector
Bare bones Pekoscope 16mm projector from 1932
Bell & Howell film cassette projector