Kevin, it's not an app, its built into IOS. you press the answer button on your BT headset and talk. IT then responds with voice responses, and you answer it. I carry both and iphone and an android phone every day and I wish the voice control was as slick as ios. I can touch my headset and say "Call Work, it responds with "calling work" and if it was incorrect I can say "cancel" like when it hears "call wok".
I can also say "call john" and it will in voice tell me, "there are multiple johns, John smith or John Doe.
I can also say at any time , "play the beatles" and it plays them "stop" will stop ,etc...
Now outside of that it falls on it's face with the failure of having to look at the screen or touch the phone. Texting is a crap shoot, and anything else does the failure that even android does, brings up something on the screen for me to look at. Having it look at anything or touch the phone it's self is a fail for voice control on ANY phone platform.
I use voice dialing with my phone in the back seat in a bag on my iphone, never having to touch the phone. I am unable to do this with android. I can say "call dave" but if there is more than 1 dave, call fails as it waits for me to touch the screen.
That is my problem with android voice control, it's not smooth at all and has no feedback at all. when I use it I have to pray it is calling the number I want. simply adding "calling dave's cellphone" when I said, "call dave" would be a giant leap for making it usable for me.