Not to sound harsh, but I don't think the blind would find a lot of use for this app...
Blind people are patient by necessity, I'm sure there are many who wouldn't mind waving around their phone scanning for text.
That doesn't rule out that text to speech with translation wouldn't be beneficial - just not in this context imho.
//Actually -- I'm not sure how limited the text-to-speech stuff is in the kindle. (as-in -- how many books in the store allow it. But on the couple that I've tested - it works great)
Also -- audible/various other audiobook retailers are great.