Google Labs is really kicking off and today brings us yet another glorious creation from the Gmail team.

According to InformationWeek the Gmail team have added the ability to send an SMS message from the chat window in the left-nav panel in Gmail. While the Gmail blog has yet to display an official announcement for this new feature, InformationWeek reports that it will be posted early today.

Further expanding the possibilities for the left-nav, (which can already include chat, calender and Docs) users can now send a message from inside Gmail by entering the recipient mobile phone number into the chat window. This in turn prompts a "Send SMS" popup menu. According to InformationWeek, Google’s texting service also assigns the Gmail user a persistent pseudo-phone number, meaning the recipient can reply to the SMS later using a consistent number.

As usual, to make use of the feature you have to go into settings and activate the SMS Labs feature. GoogleWatch got a hands on demo of the feature with Gmail Product Manager, Keith Coleman who said the addition of SMS to chat was down to people becoming increasingly frustrated that they couldn’t reply to friends who signed off mid-chat. While it seems like a great idea, Gmail warns that recipients may be charged each time you hit enter so it could be pretty easy to rack up a high bill. This feature is perfect for finalizing plans with friends who’ve been disconnected but could be costly if you use it for full blown conversations.

SMS capabilities is one of many new features to come out of Google Labs in October alone. The Gmail team tout Labs as a way to test as many of their ideas as possible with more popular Labs being considered for permanent implementation.

We’ll keep an eye on the Official Gmail blog and update when there’s more information available.