It's the app that looked like a joke: point your iPhone camera at a sign written in French and on the screen, you see it in English. It's the universal translator of Star Trek or the Time Lord Gift of Doctor Who except that it is real. Like many, I downloaded the free app just to see if it were true and it was. But you get only a kind of demo limited unless you buy packs such as English to Russian. I can't remember how much those cost but it was enough that I put it off until I was going to a country. I never once remembered to do that.
Now we don't have to: the whole thing, in-app language packs and all, is free.
It's free because the development company has just been bought by Google. The mark has turned everything free and I am downloading it all right now.
I'm sure it won't remain free for long. I'm not sure whether it will continue as a separate app, though: you can well imagine that Google is intending to incorporate this technology into its other offerings. Fine. Good, even. But the current Word Lens app may not survive so grab it while you can.