Michale Streeber reported on his blog that an iOS developer who file a bug report and was told by Apple that they have no plans to make Siri (the artificially intelligent speech recognittion assistant) available for iOS devices other than the iPhone 4. But, why is that? Is the faster processor in the iPhone 4S necessary to make Siri work well? Perhaps not.
Apple: We Have No Plans To Bring Siri To Older Devices
The answer may lie with another hardware component unique to the iPhone 4S. iFixit re-examined the components of the 4S they took apart. They noticed an infrared (IR) LED that is almost always emitting IR to see where the user is relative to the 4S. iFixit speculates this is to provide information for the Siri software to determine when you are about to ask it a question. You can watch the video embedded below for a detailed explanation.
Video source: iFixitYourself