This is fantastic, and something which I've looked forward to becoming a reality since translation software started appearing many years ago.
To allow real-time (even if it has a delay of a few seconds, it would still work) conversation between two people who don't share a language. This would've been seen as science fiction about 10 years ago.
My only concern re; the software would be (as others have asked), if it's contained in-app (which would surely be a huge task), or if it relies on Internet connection. That would cut down the benefit a little, but to many in cities with free Wi-Fi, or 3g/4g networks, I'm sure it would still work fine.
Also, I'm not sure how much I'd like the banded one of those ear-pieces to wear by a stranger - especially as I might be the 20th person that day who they'd talked to. It'd be awkward to wipe the ear-piece down, but I think I'd just be awkward and do it anyway (as an Englishman, I don't like to offend anyone). Sanitation is important, and I don't fancy an ear infection because I helped someone out.
But great tech, and if it works as well as they say, this could really catch on. Great hunting :)