Voice recognition technology is good but it's not yet as good as the human ear and can give false results. Instead the app asks learners to record and compare their pronunciation to native speakers' and judge for themselves whether they've got it right or not. This system of listening, comparing and practising works because it's very like the way we all learned our first language. Years of experience have also shown us that, although it's possible to cheat, no one does because they'd only be cheating themselves.