Cardboard apps

I've got an iphone 5, what are the best apps to see what the fuss is about with these cardboard apps, it would need to be one of those where you easily make your own view holder from like a shoebox or some shit, I am not wasting good heroscape money on a commercial holder/viewer

Isn't the Google one a cardboard viewer? It's fucking cool, Lee, I've wandered over the surface of Mars.

Be great if you were pissed as well.