Podcasting startup Odeo launched a mobile focused side project dubbed twttr this weekend. The free service brings social networking features to regular SMS. Unlike Dodgeball, twttr is not limited to a select set of cities.
twttr is accessible through the short code 40404, after registering your status is set by simply sending a message to the short code. Your friends can choose to follow your updates live (they will get a message when you change status) or only when they want to know what you're up to. Users can choose to follow all their friends live or pick and choose. There is a list of keywords used to control the service app entirely through SMS.
There is also a web based interface, which might be useful for users without unlimited text messaging plans. While turned off by default, there is a feature to share your status messages online (at www.twttr.com/yourusername).