The jailbreak tweak QuickSiri Siri tries to make something faster in one time the entire screen. On the iPhone 4S provides the tweak for a minor difference, but users with older iPhone that Siri through a proxy server benefit from this.
Keep your normal home button on your iPhone and hold to Siri to start, then a small window that the lower part of your screen fills. Only after you have spoken command Siri fills the rest of your screen, so you do your own question and Siri's answer read. On the iPhone 4S, this leads to many problems, but older iPhones who use Siri using a proxy server may stay a short time suspended between the two screen sizes. QuickSiri solves this by at once to full screen.
There are several tweaks that you can get Siri working on an older iPhone, including Spire . To use, just put a special proxy server to connect. The experimental jailbreak app Assistant Connect tries as possible without proxy, but requires that you have a friend with an iPhone that 4S has his token to share with you.