iOS: If you’re looking for a way to legally (albeit not with Apple’s blessing) get Siri on your jailbroken iPhone or iPad, Spire is a clever port of the application that downloads all the copyrighted components directly from Apple.
Two well known iOS hackers, Grant Paul and Ryan Petrich, have released a very clever work around to Apple’s restriction of Siri to iPhone 4S. Unlike previous Siri hacks/ports, this one doesn’t actually violate any laws. Spire connects to Apple’s servers, downloads the Siri components, and sets up Siri on your older iPhone or iPad as though it were an iPhone 4S.
The only catch is that you’ll need to route your Siri requests through a proxy server (they share a list of ideas to help you achieve that end).