God knows where will be the Twitter based applications in a few years from now. Already, I have seen very innovative twitter applications and tools that are developed passionate developers.
Here is one more: Twalkin! Yes, all Twitter tools start with the letter 'T' making it easy for us to spot Twitter based tools.
Twalkin enables Tweeters to talk with their followers free of cost. You only to have a telephone or a Skype plus of course a Twitter account. If you happen to have an oPhone, you can download this Twlkin application.
Watch this cute video about Twalkin.