It's Twitter.
Twitter is a "micro-blogging" and social networking site where you can send updates or "tweets" to the site through various methods including through the website itself (Twitter.com), IM, cell phone or a third-party program. Your updates are broadcast to everyone or just to your circle of friends. You can also receive your updates via SMS on your cell phone.
Instructions
1. Go to Twitter.com and hit the "Join For Free" link.
2. Go to the "Settings" link on the top of the page.
3. Select the "Phone & IM" link on this page
4. Enter in your cell phone number, including your area code, in the "Mobile Phone Number" text box and hit the "Save" button. If you wish to receive updates on your cell phone from Twitter, check the box next to "It's okay for Twitter to send txt messages to my phone. Std. rates apply."
If you're outside the US, precede your phone number with a "+" and your country code.
5. Wait for Twitter to send you a text message saying "That worked! What are you doing now?"
6. Update Twitter by sending text messages from when you're on the road, riding mass transit, waiting at the doctor's office, or whenever you're away from the computer. If you opted to receive updates, you'll get text messages whenever your friends send their updates.
Tags: your cell phone, cell phone, , from Twitter, messages from