You can download the language for offline usage, at least in android

chris_overseas · on Jan 15, 2015

That only works for the (amazing) WordLens functionality. Live audio translation still requires Google's cloud for processing.

agildehaus · on Jan 15, 2015

WordLens works offline without any additional downloads, at least for the languages I tried (Spanish, French, English).

Audio translation and TTS works offline if you have the proper languages downloaded, but being able to detect what language is being spoken seems to be an online-only feature.