iOS: Yes, you read that right. You can learn a new foreign language (currently, Spanish) by doing something you might already be doing regularly: browsing internet cat memes.
This is likely the most entertaining way to brush up on or pick up a new language, but there's also a lot of science behind it. CatAcademy ($0.99 in the App Store) was started by Ed Cook, a co-founder of Memrise, a popular language-learning tool. It incorporates Memrise techniques, such as spaced repetition, multiple test modes and adaptation to your progress.
The cat photos serve to create a strong association between the phrases and their meanings. Research suggests that cuteness, humour and strong visuals make things more memorable. And who doesn't enjoy tapping on lolcats? (Except the text in this case is actual conversational phrases.)
The first app available is Cat Spanish, but there are more in the works. As you tap away on the cat photos, you'll be quickly brought up to speed for conversational Spanish. I already know some Spanish, but I downloaded this anyway, because cute cats.