This showreel by Robb Montgomery was filmed in London during the last week of September, 2015 with an iPhone 6 Plus.
There has been no color grading or any other advanced processing of the footage by any other device. This reel contains essentially raw footage. Albeit of a high quality.
All of the shots were filmed handheld and all clips were trimmed and assembled entirely on one iPhone 6 Plus.
Be sure that to enable the "HD" button or option in the video viewer when watching these clips.
The film reel below was made by AmnesiArt, a studio in France that produces film and photography.
This is what the new 4K iPhone 6s model can do.