In iOS 8, Apple introduced the “Hey Siri” feature similar to Google Now, which could work without pressing a button
AppleInsider reports that iPhone 6s and iPhone 6sPlus, which is expected to be unveiled in less than 24 hours, will be unveiled with the constantly active “Hey Siri” feature. The function will be very useful while driving.
It is not yet clear whether this function will be available on other iOS devices, since in the latest update to iOS 9 beta this function did not work without connecting the device to a power source.
Since we do not expect iPhone 6s or iPhone 6sPlus coming out with some major battery improvement, it’s entirely possible that Apple will make this feature available at least for devices that were released last year.
If you have jailbroken on your device, then you can activate the permanently enabled “Hey Siri” function by installing the free UntetheredHeySiri tweak.