My main out-of-home way of interacting with Twitter is through the Tweetie application on my iPod Touch. And one of my favourite features of Tweetie is its ability to automatically translate tweets from other languages.  All I need to do is “swipe” the tweet in question, which calls up a set of icons; I click on the right-most one, click “Translate” and the tweet appears in English (or at least in Englishish) in a pop-up dialog:

Bonus tip: on an iPhone or iPod Touch you can take a screen shot by pressing the “sleep” button (on the top of the device) and the “home” button at the same time; the screen will flash briefly to show you that you’ve succeeded, and the next time you sync your device your screen shots will appear in iPhoto for download.