Well, I realize this is iOS 7 forum, but I started using it more once upgrading my phone to iOS 8. When the phone is connected to a power source, simply saying "Hey Siri" activates Siri (need to change General | Siri | Voice Activation). I can now ask Siri "what time is it?" in the morning or say things like "tell my wife that I will be home in 15 minutes" or "remind me to pay the bill when I get home" while driving.