This made me ask, is there a (perhaps Swift) API to get the raw pixels coming in from the camera, if there is such a thing? I mean, before any processing, etc.

There is. If you use lightroom app for example you can have access to raw pixel. But I'm not sure there is a way to get all the images the camera app from the iphone take. Phone don't take one shot to create the final image. they take hundred of shot and combine them.