It"s tough to say exactly why you would need this, but it looks like it could be a real thing if a newly emerged video is to be believed. Although there isn"t a proper model number to identify the phone, the handset looks quite similar to the widely leaked nubia Z18s. If this does arrive to market, it will be interesting to hear what nubia has to say about its design. While this might be a bit much, we have seen dual screens used for phones in the past, with a more recent example being Meizu"s handset from last year.
Again, this could just be some kind of demonstration unit but the similarities with nubia"s model are uncanny, which could mean that it might arrive to market soon.
Source: Weibo via Phone Arena