I saw that a few days ago when the filmmaker first posted the video. A woman walking along and shading her eyes from the sun is not a cell phone, even in 1927. If it was a time traveler, she could not use a cell phone without towers, and would not need a cell phone because they have universal implants that operate off of biorhythms to communicate.
(Please do not ask me how something can operate off biorhythms, I stole it from a lame idea in an episode of Smallville.)
The picture was very fuzzy and it was not, I repeat, not a cellphone. Time travel is a very stimulating idea but far from the realm of possibility. What has happened is over, yet the future is not set. Look at the original picture.