Three groups participated in a study on the added value of mobile technology for learning English as a second language for primary school students. The first group had classroom lessons in English about zoo animals and their characteristics. The second group took classroom lessons and worked with a mobile application on location in a public zoo. The third group received the same treatment as the second but, as an extension, was allowed to take the mobile application home for a fortnight. A pre- and a posttest were conducted to measure the individual change in mastery of a set of targeted English words. The results showed that the group which took the mobile phone home improved the most. However, when the additional learning time, spent apart from school, of this third group was controlled for, the superior performance of the group disappeared. The results indicate that students are motivated to use the application in their spare time and that this benefits their learning. The conclusion is that formal school learning can be augmented by learning in an informal context, away from school.