When Siri was launched for the iPhone 4S a lot of people were disappointed that their older iPhones weren't able to run the app despite them being capable hardware wise. Since then, a lot of similar apps started popping up on the App Store claiming to be capable of doing what Siri does - even on the Android Marketplace. Today, one of the most popular voice assistant apps for Android, speaktoit, is now available for iOS devices as well.
Ubergizmo, speaktoit now on iOS