Been playing for the last couple of days with an IOS 8 feature whereby Siri is always listening for you to say "Hey Siri" and before you Android boys wade in, yes I KNOW it's a rip off of Android, but that doesn't stop it being a nice feature and well implemented.
I drove 200 miles on motorways yesterday at 70mph (or so) and it didn't miss a beat. Didn't trigger spuriously even once, and never failed to pick up my Hey Siri.

Waits for Apple to sue Google for its implementation even though that came first....

On a serious note works well on Android too.... can use it on the S5 to call/text etc

"Okay Google, upgrade to iOS8"

I find that Google Now occasionally triggers by itself due to background noise from the TV or radio.

It's still very early technology but some things are now quicker to do by voice than to use the screen. "OK Google, set alarm for 7am" is much quicker than going into the Clock app and setting the right time for an alarm. Asking it to play a specific song or band is much more hit and miss.

I agree, I have used Siri for setting alarms since day 1.