Google Translate for the iPhone has been specially optimized for speed so you don’t have to wait a long time on uncertain wireless connectivity in front of the waiter who speaks nothing else but German. In addition to the speed Google Translate also supports all existing language pairs that are supported on the web based version of the translator, and uses a client-side data store to store past translations on your iPhone. This enables you to have the previous words and phrases on your device to access them inside a Metro tunnel with limited connectivity to the outside world.
The web app is cleanly laid out, with selector menus for the source and target languages, a field for entering your phrase, and an arrow that lets you toggle which direction the translation goes. Best of all, the Google Translate web app stores your recent queries, so you can load it up with a few handy phrases and not worry about erasing the earlier ones when you add more.
You can try Google Translate for iPhone, by point your iPhone web browser to translate.google.com.