Neat idea. But also, somebody's definitely going to take some kind of inappropriate picture <i>just</i> as the charge runs out, and will be stuck with it at the worst time. And somehow this makes it even better.
Hmm, what's the purpose of this? It's a cool hack, but waiting 30 seconds to see the photo I took doesn't really give me anything more than the camera I already have.
I think this is really interesting. I think you could make really cool actual black and white polaroids with eink displays in a 3d-printed chassis. Though way more expensive...