is it possible to create a magic shutter as they have on the iPhone app ? https://itunes.apple.com/us/app/magic-shutter/id408256708?mt=8
http://petapixel.com/2010/12/22/watch-long-exposure-shots-develop-before-your-eyes-with-magic-shutter/
Possible? yes. At real-time speed? I doubt, but 1fps or 0.5fps should be doable. Image quality? I doubt it will compare with a proper long exposure, but it will have a little more DR and it can also work for long exposures in daylight.
But if anyone gets bored and wants to code something cool, start tweaking the silent picture code. I actually have a half-working patch written a few months ago - it only needs some display filter trickery, fixing the vertical banding, and optimizing it for speed: http://a1ex.magiclantern.fm/bleeding-edge/silentlongexp.patch