Send SMS in Gmail Chat

Gmail’s Labs have a new feature called “Text Messaging (SMS) in Chat”. Enable this, and you can send around SMS straight from Gmail Chat, Google says... at least to US phones. Google writes: “On the receiving end, when you get a text message from Gmail on your phone, it will come from a number in the 406 area code. (...) You can reply to this text on your phone just like you’d reply to any other text. The reply gets routed back to our Gmail servers and shows up in your friend’s Gmail chat window.”