Kicking off our TNW Europe 2014 conference in Amsterdam this morning, Duolingo co-founder Luis von Ahn announced the upcoming launch of its Duolingo Test Center, a new standardized language test that you take on a mobile app.

In order to verify your test results, the app will monitor you by using your camera and microphone and ask you to stand in a corner to make sure no one is behind you feeding you answers. Duolingo will use human proctors to ensure that you’re playing by the rules.

The test will cost $20, as compared to $300 for equivalent in-person certification tests. Duolingo plans to launch the service in three weeks.

IMG 1155 730x547 Duolingo announces Duolingo Test Center, a $20 mobile alternative to standardized language tests

Duolingo now boasts 12.5 million active users, giving it a broader reach than the number of language learners in the US public school system, according to von Ahn. The service is able to offer free language lessons on the Web and mobile apps by using its students to crowdsource translations for publishers.  The model attempts to create a win-win situation for everyone involved: students get to engage with real-world content, publishers get their work translated and Duolingo generates enough money to keep the service free.

von Ahn came out of retirement to create Duolingo after Google purchased the reCaptcha technology he helped create. The common thread between Duolingo and reCaptcha is the effort to harness human time and energy in order to solve problems. von Ahn said he felt guilty about the amount of man hours that had been wasted on captchas, so he began using the system to digitize books.

If you’re not excited about Duolingo already, you should be. By offering free, practical education, the company has the potential to improve the fortunes of millions. von Ahn estimates that 800 million of the 1.2 billion foreign language learners around the world come have three traits in common: they come from low socio-economic classes, are learning English and are studying for work reasons.

Head to our TNW Europe 2014 page to keep up with the rest of our coverage of the conference this week.

See also: Language-learning platform Duolingo wants to be a game, which suits its next target: Asia