1- Does it upload/download anything?
I think that I did not see any network traffic when selecting the video nor when saving it, but I might be wrong => if that's correct you might want to state that, as users will be happy to know that they won't need to use hundreds of MBs of cell data and that their private videos will still be private. If that's true then you might change as well the button "Download video" to "Save video" or something similar not involving "downloading" anything.
2- You might want to specify if there will be a quality loss (transcoding) or not (original audio/video codecs & frames left untouched).
Cheers & good luck