I was wondering what twitter widget is used on the demo page?
For the demo site, I simply used a widget from the official twitter website, it’s very easy to customize the look & feel on the spot on their website. Here’s the link: http://twitter.com/goodies/widget_search
Then just copy and paste the js code into a text widget in my theme.
You can choose different twitter goodies here: http://twitter.com/goodies/