You could fill a weather balloon full of helium, attach an iPhone, release it and let it float so high the iPhone films the curvature of the earth. After it bursts, retrieve the iPhone via GPS.
Some Boston students did it and got footage including the curvature of the earth and the deep black of space.
http://news.sky.com/story/1295234/science-students-launch-iphone-into-spaceThis is a picture their iPhone took clearly showing the earth is not flat.

Why is the horizon line flipping, once its curved, then after the camera rotates/flips a bit its flat, or its curved in the other direction?
What causes that flipping? It is very strange.
I`m no expert in perspective and geometry but i`m just curious. Can somebody explain please?
Because a fish-eye lens is used, like gopro cameras or plane windows have the same effect.