Proving necessity is the mother of all invention, Google’s mobile team has developed an iPhone interface for Google Translate.

Allen Hutchison, a software engineer at Google, said that while planning a holiday in Europe he was frustrated that Google Translate didn’t work well on the iPhone and teamed up with a fellow Google engineer, David Singleton, to create a new iPhone interface for the translator.

He says Google Translate for iPhone is optimised for speed, supports all existing Google Translate language pairs and uses a client-side data store on the iPhone to hang onto past translations to keep them at hand, even if not connected to the internet.

The software interface was written using the AJAX Language API.“I tried an early version of this interface out on my trip and it was great – although my pronunciation wasn't,” Hutchison said in his mobile blog.

“So every now and then, I would just hold up my phone to let people read what I couldn’t. If you’re wondering about data costs, I found I could get between 200 and 400 translations in 1MB of data download.

“Although we don't charge for this service, your carrier may charge for the data usage, so be sure to know what your roaming rates are. For my plan, I found that I could translate 400 phrases for less than US$10 when roaming internationally,” Hutchison said.

To try the Google Translate for iPhone, point your iPhone to www.google.com and choose the ‘more’ tab or you can go directly to http://translate.google.com in your browser.