Black Swan is an Google Voice weblication, this means it is not something you can purchase in the iTunes App Store or Cydia. This weblication looks and act like a real iDevice App, but its just a link on your home screen that links to a Safari website.

Black Swan is a feature-rich weblication that enables you to view and manage your Google Voice data just like a native iPhone application. It has been available in beta mode for the last view months and has just been officially launched. » Black Swan Brings Google Voice to the iPhone