i just heard about this from a friend and got so excited at the potential, because this is something i've been wanting to be able to do forever. a company just made it so you can watch any youtube video with audio description. i just tried it and it works pretty good. not perfect, but much better than nothing. you just go to any youtube video and type "www.viddyscribe.com/ " in front of the URL, and it will open on their website with audio descriptions added.
my friend said that they have another app where you upload your own videos, and that works a lot better. i haven't tried so i don't know if i can vouch for that. but it's the same people who made speakaboo which i use everyday, so it is probably pretty good.