Only for American phone customers.

Awwwwww I'll have to wait before google can customize adds specifically from my sms chats 

*sad face*

"Google SMS is currently not available in the UK." -
http://www.google.co.uk/sms/

Thanks for the article. the service is only available in the USA at this time. I am in canada and its not an option yet. You will not get the tab for sending text when you type the telephone number in the chat box and it can not be added from the "lab" tab. Not sure when it will become available but would certainly be interested to know. Thanks

Don't think is available in the UK yet!