Twwetie?
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:
American Idol
app store
Blogs Losing Chris Brown
full moon
Happy Holi (sic)
iPhone app
iPod Touch
Jimmy Fallon
Jon Stewart
Mind-boggling stuff, I'm sure. And it doesn't get any better, believe me.