Just came across this site www.twitter.com
From the site:
About using Twitter on your phone
Twitter really shines when you're away from your computer.
By hooking up your mobile phone, you can receive updates from those you're following (or just some people) when you're waiting in boring lines. And you can send updates, like"OMG, there's a monkey walking down the street!"—which, lets face it, you're unlikely to see while you're indoors.
It's all done through text messages (aka "sms"), which you probably use all the time anyway, so there's not much to learn.
Twitter doesn't charge anything for this, but be sure to know what your text plan looks like with your wireless carrier.
Also know that you can shut text messages from Twitter off at anytime by replying with "off" (and back on by sending "on"). And you can even specify that it turn off automatically at night.
Ah! well time will tell!
Twitter can be addicting, so check your plan to make sure you don't get a huge bill.