How to get siri on iphone 3gs without jailbreak?
Presently it is not possible to do this, although developments are underway that will make it possible for individuals to this without jailbreaking. If you have a different iPhone apart from the iPhone S, it is impossible to install it without jailbreaking but in its place you can use Siri cravings, which is one of their recent applications, which works in most iPhones. For more information about this application, you can visit http://jaxov.com/2011/12/voice-actions-siri-alternative-for-non-iphone-4s-devices-no-jailbreak-required-itunes-link/.
You don't want to.