For many spouses, smartphone use is a point of tension. But for David Duda and Hong Liang, a couple in New Haven, Conn., the technology is so essential that they own eight external battery packs. If their phones die, so does their ability to communicate. Mr. Duda, 62, speaks English, and Ms. Liang, 57, speaks Mandarin. They rely on a free smartphone app from Microsoft, called Translator, to render a text translation of what they say — like movie subtitles but for daily life.
