It's surprising how much I both love and am bothered by the new Hey Siri feature. It offers what's probably the best and the worst of all iOS 8 features at the same time. So what's this dichotomy? How can I be so split down the middle about this? Let me explain.
iOS 8's new "Hey Siri" offers a voice activated prompt. If you're driving and your iPhone is connected to a power source, or if your iPad is charging across the room, you can shout out "Hey Siri, set a timer for 3 minutes" and Siri will do exactly that. A few minutes later, your device will beep and you'll know to take the eggs off the stove.
"Hey Siri" is great for quick calculations ("What's 371 divided by four?"), for shazaaming ("What's that song?"), for requesting songs ("Play something by Josh Turner"), for directions ("How do I get to a gas station?") and so forth. The hands-free functionality is amazing.
At the same time, you have to be really really careful about where and when you deploy "Hey Siri". I can't tell you how many times I've been talking on my landline and Siri pipes up and offered to run a web search based on my current conversation. It's a little embarrassing when chatting but it can be quite serious in professional meetings or with privileged conversations such as in a medical setting.
Fortunately, you can easily disable voice-activated Siri. First, just unplug your device. "Hey Siri" is currently limited to power-tethered use. Second, you can override Siri by hopping into Settings > General > Siri > Voice Activation and toggle the option to OFF. This is a feature that really should have been placed into the Control Center -- I encourage you to file a feature request to put it there!
But once you're back away from those possibly awkward moments? Turn that feature right back on because Hey Siri is a real favorite, warts and all.