Try Google Translate - I assume that's what Jazz is referring to. When you select the camera icon, it will recognise and translate any Chinese characters and replace them live on the screen. I've used this quite extensively in China (was surprised they hadn't blocked it - perhaps it was working offline) and it certainly came in handy. The translation seemed to vary depending how close you held the camera (how large the characters) and some of the results were pretty amusing!

You can also use the microphone for input but you might run the risk of getting punched, molested or arrested, depending where you use it.