This would be more interesting if we didn't pay 40 cents every time I sent Emily a text message.
As it is, the most curious part is how they enable Gmail to receive SMS messages ...
Official Gmail Blog: Really new in Labs this time: SMS Text Messaging for chatMy interpretation of this cryptic announcement is that the first time you use Gmail to send an SMS message, your Gmail identifier is assigned a unique 406 phone number. From that moment on SMS to that number go to Gmail.
... 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...
... messages will come from a [unique] 406 number so you can reply to any message and it will get back to the right person. Messages from the same person will always come from the same number, so you can even bookmark it in your phone....
Makes me wonder if there's a GrandCentral angle to all this.
It's not clear whether other phones, with whom you've never communicated, can use that unique number to send Gmail an SMS.
From my perspective this is backwards. I want Google instant messaging on my iPhone, I don't want to bother with SMS at all.
Update: Chris, in comments, notes that 406 is Montana's area code (I also had a 404 typo I've corrected). They chose it to get lots of free numbers.