From the ticker, you can't. Twidroid is the only one that has been given the ticker API. I'm using tweetcaster. But, I just access it from the widget on one of my home screens. If you simply want to view the tweet, and not respond to it, you can expand the ticker feed (the little notepad icon on the right side of the ticker), go to all or SNS, and long press the tweet you want to see. It'll show you the whole thing. You just can't reply, retweet, or anything else. But, as far as accessing any other twitter app from the ticker, it won't happen til samsung releases the ticker to some more 3rd party vendors.
