There’s no way this would work, or work more reliably, than the translator apps we have on phones. In order for this Babelfish sci-fi interface to work, the other party has to be aware and pause their speech for the translation. If they can’t hear their translated message they’ll speak over it. Either that or you have some kind of deafening that passes-thru the translated voice in realtime, and then you lose their emotion, emphasis, and tons of other information that doesn’t fit neatly into the standard monolingual worldview of tech.
Even the “conversation mode” built into Google translate or the iPhone app is useless. I can only imagine it working in the sterile environment it was probably designed in: a conference room with two people trying there hardest to make it work.
I live abroad and travel a lot for photography. Whenever I’m using a translator app, it’s typically a chaotic situation like haggling with a taxi driver, a meal with a group of strangers who invited me to eat with them, lots of background noise. The mode that everyone defaults to, without fail, is to use their own phone to speak or type a message and then hold it up in front of their interlocutor’s face. Sometimes they mix in some fragments of English or I know some fragments of their language. It’s lossy but it works.
I can’t imagine a wearable that would perform better. A notepad that can magically translate little messages is about as far as I would want it to go. Tech is pretty awful at intermediating human relations.