SOFTENSTORM's LIVEBOOK is a free dictionary app which uses a rear camera to scanning texts, capture and lookup words in its dictionary, and translate the definitions using a highly sophisticated translation engine from Google. If you know a "pen scanner" before, this is the same but more enhanced and works on the iOS platform.
It's a free scanning dictionary app among other text recognition ones that can assist students and enthusiasts to learn new words from texts but doesn't ruin their English learning habits. LiveBook's dictionary has more than 150,000 words including technical terms and phrases.
You can use SoftenStorm's LiveBook on an airplane or even in a rural area because it doesn't require the internet.