Official Gmail Blog: Really new in Labs this time: SMS Text Messaging for chat - http://gmailblog.blogspot.com/2008...
SMS is back in action after a brief prior launch. I use this feature all the time when I am late for meetings -- since it reserves a unique phone number for each contact, I just text something like "10 mins late" to the Gmail SMS number associated with someone in the meeting and it shows up in their Gmail account. - Keith Coleman