Hacker News Reader

It's, IME, very common for immigrants (especially those that immigrated in middle age) to be intelligible to native speakers when speaking the local language, but have more trouble understanding native speakers. So one-way translation may be useful.

(OTOH, it may also mess with code-switching.)

Really? I have found the exact opposite. You can pick up a lot of clues from words, expression, tone, without knowing the entire sentence. But that doesn't help in talking to them.

That's the reverse of the common case -- it's much easier to learn receptive language than expressive language.

you use your phone's speaker. this is shown in the demo.

I would answer in my own language, and let my interlocutor's device translate for me instead.

Buy two pairs :)