Exactly. I've been taking Japanese recently, too, and the grammatical structure of the language alone is enough to show that the "real-time whispering earpiece"

Exactly. I've been taking Japanese recently, too, and the grammatical structure of the language alone is enough to show that the "real-time whispering earpiece" as an impossible concept: in English, the verb usually comes near the beginning of a sentence. In Japanese, it's near (or at) the end. Translating one language to the other therefore requires a mental "tape delay", while you map the one grammar onto the other. Even when you hear bilingual, fluent translators converting Japanese to English, there's often a weird disassociation between the words the speaker is using and the words coming out of the translator. The translator is buffering the words and translating in logical units. Even if you grant the benefit of the doubt and call this "real time" translation, I know of know translation system that is capable of any sort of similar kind of judgment with an unbounded input stream. Deciding where to begin/end translation requires knowing what the original sentence intended to express. And computers still suck at that.