With the release of iPhone 4S and Siri, many users of the previous generation of the phone looking for an alternative to this incredible feature.
Navigating the App Store you can find several applications that are similar. One of the best is Vlingo, a personal assistant with voice recognition.
The best thing about this app is that it is free and allows you to:
a) send text messages.
b) send emails.
c) call the contacts available on the agenda.
d) search the internet.
e) updating your Facebook status.
e) sending tweets.
Requires no adjustment and has a good system of recognition. A good recommendation while the Dev team, responsible for the jailbreak, brought it as a tweak to the iPhone 4 and Apple devices.