Echofon, a full-featured Twitter app is now available for multiple systems as a free download. Echofon automatically keeps your unread tweets in sync between your Mac, iPhone, and iPad.
Quickly view Photos, Videos, and links, and recieve notifications of mentions, and messages - you can even put it to sleep. Echofon is for Firefox 3.0 or later, Mac OS X 10.5 or later, and for Facebook users in the App store. Download Echofon Here