I just downloaded the app to my iPhone, and it works impressively well. The app is free with a demo mode that reverses words, and language packs are $5. The best part is the whole app works offline, so it works, you know, when you actually need it.
I did buy the Spanish to English pack for emergencies, but this picture is really fun so I'll post it instead. Can you read it? (iPad is apparently not in their dictionary.) Note the crazy angles and it even got my keyboard keys!