Mitzuli is the best translator app I have come across. There are hardware tools that have amazing features to allow multi-lingual communication. But they are not some open source apps.
With Mitzuli, you can input voice or take a picture of what you need to translate and get results. There is already 50 languages and they promise more. People who travel are going to find this app massively helpful.
Thanks for bringing this to my attention. I prefer open source apps as well as ones that work while offline.
(Update) I just checked and it appears that the Mitzuli app has been removed from the Google Play Store.