I've just installed Twitterator on my iphone and you can actual "Tweet" your location. So anyone following me can determine my location if I decide to let them know. Just click on the rightside of this blog or click HERE I AM.For all you blackberry users, you can use an application called "Twitterberry". Download the application here:Twitter for Blackberry
Once you learn to use twitter online you will definitely be hooked on Twitter on the phone. Enjoy!