I got the stock 4.3 android camera, 4.4 doesn't work well on the s3.
It would be a tad smaller than the s3, but not much. I can comfortably use the s3 with one hand, once I cant do that then I'd say it's too big. Which I'm thinking might be somewhere around 5in for me. But that's the great thing about "fragmentation", plenty of flavors to choose from.