Here's the "Z'Smart mirror smartphone case". And it was most likely designed with vanity in mind. Sure you can always carry an extra mirror in your bag, but why go through the trouble of looking for it when its connected to your phone?
The pivoting mirror attachment on the back of the $20 case is only going to appeal to those who need to look in the mirror every five minutes. Check out the links below for more product information.
Wired has published a very nice feature on Kip Thorne and the science behind Chris Nolan's Interstellar. Kip Thorne is one of the world's most celebrated theoretical physicists. He and Nolan worked together to ensure depictions of scientific happenings in the film are as accurate as possible. Read more