Location finding service for expats (Beijing)

Dear all!

Yesterday a friend of mine mentioned that there is a phone service in Beijing (some mobile phone number) you can send a message to with the name of the place in English or pinyin and they will reply you back in characters so that you can show the address to a taxi driver. Has anyone heard of such service? If yes, it would be great if you share the info concerning the number! Thanx in advance!