Now you can send free text messages to US phone numbers from anywhere in the world right form the gmail chat(The receiver may be charged each time you send SMS by their moblie carrier).If your friend is offline you can keep in touch with him/her through this gmail service.To enable this service click on settings in your gmail account ,goto Labs ,then scroll down until you see "Text Messaging (Sms) in chat" ,enable and save changes .Type in a phone number into the search box in the chat window on the left then click :send SMS" to send message