I've been using WorldLens [0] for several weeks and while it has an inferior UI and its translation engine is outright dumb, it works offline and it's a HUGE plus. One needs this sort of app when traveling in another country, so the chances of having WiFi/3G connection are pretty slim, so no Google translation for you.
That's not to say that's Google's take is wrong, it's just (far) less practical right now.
"One needs this sort of app when traveling in another country, so the chances of having WiFi/3G connection are pretty slim"
THIS is what needs fixing. In Asia, it's often cost-effective to get a Sim on the spot (I got one in Kuala Lumpur just for a two-day stay). Usually though it's not worth getting a local Sim unless you're there for at least 4 or 5 days and that's assuming they don't insist on residency like they sometimes do.
I'm from the UK and in many European countries I can just use my own Sim without it being completely prohibitively expensive (although it's still a complete rip-off).
But we need decently, priced roaming data or quick-to-buy local SIM cards in every country so that all those maps, translators, local guides and other marvellous aids to travelling can actually get used.
Perhaps more for the tinkerers and enthusiasts, but https://github.com/arinkverma/Apertiurm-Androind-app-devlopm... (yes, it's misspelt twice) runs the full Apertium translator offline on your Android device. Apertium is more aimed towards post-editing (for publication) of translation between closely-related language pairs (rather than gisting/translation-for-understanding), but lately there have been some more distant language pairs which would be useful in a phone app.
That's not to say that's Google's take is wrong, it's just (far) less practical right now.
[0] http://questvisual.com