You can download the SDL Translate apps for Android or iOS. The apps are easy to use and have great features such as Chat (iOS only), Text to Speech, Speech to text, Introductory phrases (no connection needed), Translation history and Favorite Translations.
Get SDL Translate for Android
Get SDL Translate for iOS
You can also use the mobile version of FreeTranslation.com by accessing m.freetranslation.com on your device.