The term "centripetal" refers to a force that makes a body follow a curved path, and in this case, an iPhone 6 is that body. "Centriphone" is a play on that term, as an orbiting iPhone shoots super slow-motion footage of a skier at the center of its path, as they cut their way down the side of a snowy slope. This clearly takes selfies to the next level.
Nicolas Vuignier is a professional freestyle skier from Switzerland "with a passion for technology and filmmaking," as noted in his YouTube account description. In the above video, it shows Vuignier using what appears to be some thin string, perhaps fishing line, to support his iPhone while extended, swinging the extended line out above his head in a circle, creating this dramatic effect. It's reminiscent of the bullet-time effect from The Matrix, which took many cameras and an elaborate setup to capture.
Vuignier has a few other interesting videos on his page, which of course involve skiing. Here's one below, where he placed emergency flares on his skis during the night, resulting in this piece.
We reached out to Vuignier for information on how he did this, as alluded to on reddit and in his video's description he teased that, "A making of is in the works," but as of the posting of this article we have not heard from him. Be sure to check out Nicolas Vuignier's YouTube to catch it when the making of video drops.