SMS Text Gmail Chat (US only)
How it helps do no evil: Gmail automatically sets you up with a Gmail Chat widget that lets you send your Gmail friends instant messages. But often, these contacts either leave their computers to run to the store or out for lunch.
You could send them an email, but not everyone owns a smartphone with email. But many of those people have SMS Text, at least. As a result, this add-on is handy because it allows you to send an SMS text message to them from your Gmail chat box.
How to set it up: There is a little legwork involved after you click to 'enable' SMS text on the Gmail Labs page. After you enable it and click save, return to your Gmail inbox and go to the chat widget (it's on the left column of your Gmail by default, but there's actually another feature in Gmail Labs that allows you to move it to the right side if you wish).
Go to the search bar in the chat widget (it says 'search, add or invite'). In that field, begin typing the name of the desired contact. Once the name pops up, scroll down to the name. Once you scroll over the name, you'll see an option that says 'Send SMS Text'.
From there, add and save the number for that contact. Now, go to that person's name on your buddy list in the chat widget, and you'll be able to send him or her an SMS Text.
Above is the SMS Text Gmail Chat Window.
Doing No Good: Be mindful that normal text messaging fees apply for your recipient, and that only US phones can use this feature for now. Because SMS texts have 160 character count, it would be nice to see a character countdown as you type the text (like you would on Twitter).
Also, when you receive a text from a Gmail sender, a random phone number appears (we presume from wherever it gets routed). When I sent my colleague and mobile expert Al Sacco a text message, a Montana-based number appeared in the message on Sacco's BlackBerry screen. This could throw off a recipient who doesn't memorize your number (since my number, for instance, is a San Francisco-based 415, and calling me back at this Montana number would be useless).