Notice the "...and drops a coin..."? More about the Notificator here and a web version here.

The only business model I see in Twitter (and its ilk) is of being bought by one of the big fish, perhaps for their data. This is probably why they're in no hurry to reveal how they're going to monetize the site. They're perfectly willing to ride the current wave of buzz in the mass media until some sucker shows up with wads of cash.