A startup called Waverly Labs is developing Pilot, a set of smart earbuds that translate between users speaking different languages. This translator wearable works in conjunction with a custom app that utilizes speech recognition and machine translation to help you communicate. These are a potential travel winner.
The complexities of the human vocal range are an amazing thing. Take a listen to this segment from The World, and a rare look at what the mouths and throats of a beatboxer and soprano look like while they are performing, part of learned speech functions that as it turns out, are very similar to that of learning various language skills.