Siri is a new feature introduced exclusively in Apple iPhone-4s (some folks managed to get via a hack in Apple iPhone4) in October 2011.
Siri is a personal assistant in the iPhone which helps to control iPhone via voice commands. More similar to Voice Commands feature found in Android Phones like Galaxy S2.You can schedule a meeting ,call a person by telling his/her name, and text to someone – all can be done ,using your voice in Apple’s Siri environment .
The Practical Issue with Apple’s Siri
All the commands you give should go to the Apple’s web servers to get processed and return to your phone for the action(Android does the same ,using Google’s servers) . This process makes the data usage almost double comparing to the previous data usage records of the Apple iPhone 4 Owners and triple when you comparing with iPhone 3G a study reveals .