Don't know about Tweetie, because I've not tried it. I have, however, had an app called "Twitter Trend" on my iPhone for several weeks now, and it displays, you guessed it, Twitter trends. And it's free.
Don't get too excited, though. Not only have I never seen the F word on it (although I must confess that I don't look at the app very often), not even the A word, but if you're looking for something interesting, you're going to be sadly disappointed. As i write, these are the top few entries on the "Hot" list:
Blogs Losing Chris Brown
Happy Holi (sic)
Mind-boggling stuff, I'm sure. And it doesn't get any better, believe me.