That's what my Galaxy S5 does. I do have to unlock the phone, but you hold it over the reader and the app comes up. The only thing that slows me down is when the payment terminal asks irrelevant and/or annoying questions. When I was at the vet the other day it wanted to know "Credit or Debit"? WTF? And at the grocery store it wanted to know if I wanted cash back. If they stop asking questions like these, the transactions would be quicker.
My preferences (excluding online purchases) are:
1) EMV credit card.
2) NFC via Wallet.
3) Cash.
4) Write a check (rarely)
I refuse to use my debit at any machine other than an ATM, and even then I am picky about which ATM machines I will use. If the crooks get your debit card number, they can create all sorts of headaches for you.
I used to use the normal credit card swipe for some things like gas stations, but I had my card # stolen at either a parking garage or a gas station, so from now on it is cash all the way for those things. Yeah, it is a pain, but I am still pretty steamed about the horrible cyber security at some of these places. If the attendant steals from the till or the store gets robbed - well, that's not my problem. If they want fewer cash transactions, then they can add support for #1 or #2.
People say you have no liability if your card gets stolen, and while that is sort of true, it can take several weeks before you get a replacement card unless you insist that they overnight the thing to you (like if you are on the road somewhere). My card was stolen on the 6th of the month, and the replacement *finally* arrived today. I had called to complain last week about why it was taking so long - apparently some nonspecific upgrades to their system caused the request to be stuck in a queue for 10 days. And it was a pain in the interim. Check into a hotel - do they take AMEX, or not? Pay for car repairs - they don't take AMEX, so I had to write a check to the guy. I could try and get yet another card, which I wouldn't need/use once the replacement arrives, and realistically the other card wouldn't have arrived before the replacement.