RTranslator is a simultaneous voice translation app based on Google APIs for speech recognition and translation.

To use it you have to connect to someone who has the app and start talking, the phone of the other person will repeat what you are saying in his language and, when he talks, your phone will do the same thing in your language.

You and the other person can also connect a Bluetooth headset to your phone and put it on standby in your pocket, in which case the app will continue to work normally and the audio will be captured and played from the headset.

The Google APIs are not totally free, and to use this app you have to configure it, please follow the tutorial in the GitHub page.