Found the setting in gmail under settings/labs/Text_Messaging(SMS)_in_Cha
Where you can send and receive SMS messages in Gmail, Its not perfect you loose the reply if you have closed gmail, and you have to have their mobile phone number in Gmail.
Ive had various ways to email SMS messages, and to get messages via email, but its kinda neat to have something that actually works bi-directionally.
People can sms that way without incurring fees, atleast on the gmail side (obviously the person on the phone may get fees, so before you go hog wild make sure they are ok with it!, but even if you are not ok, you can block either that user or all of gmail sms)
