Speech translation works well but needs data connection
I just installed this app (pro version). I tested with German, French, and Portugese. It was very accurate with recognizing my voice in English, French, and German and translating to those languages. I only tried simple, traveler phrases.
A serious problem is that it does not work without a data connection. That is fine in your home country or perhaps in a hotel with wifi. But often you will not have a data connection in a foreign country. So, no way to talk to the taxi driver in Sao Paolo.
One workaround is to record the phrases you think you need for the day when you have a wifi connection. These can be played back without a data connection. But you still won't be able to translate the reply.