Google officially launched Android Pay about a week ago, rolling out its challenge to Apple Pay to a small selection of phones, cards, and places you might use it.

In this week's Tap That App, we test drive the alternative to tapping your iPhone at the cash register: doing the same thing with your Android smartphone with Android Pay.

Setup

Android Pay, just like Apple Pay, works only on smartphones with NFC and also requires Android 4.4 KitKat or later, so if you're using a smartphone that's more than a couple years old, you might be out of luck.

However, most newer, higher-end Android smartphones come with NFC and KitKat, and by the sheer numbers, Android Pay will be open to a lot of people. But speaking of exclusivity, Android Pay at least doesn't require you to own one of the last four iPhone models (including the "Plus's") in order to tap and pay.

Since the service is brand new, it's still rolling out to various devices, so we used a Nexus 6, which automatically updated with Android Pay over the weekend, for good measure.

Setting up Android Pay was really fast. You use a Google account -- likely the one you're already logged into the phone with -- and if you've ever linked a credit card, say, to buy an app on the Play Store, the only numbers you'll need to enter are the three digits of your security code and a custom Android Pay pin.

You'll also be required to set a secure lockscreen for your phone, which is a pain to get used to if you've never used one, but of course makes sense from a security standpoint. The fact that any device that can support Apple Pay by definition also includes a Touch ID fingerprint scanner counts as a point scored for Apple's side.

Availability and Test Run

The ongoing challenge facing Android Pay and Apple Pay right now, though, is the availability to use a tap and pay system out in the real world, which is still selective, though on the rise for both systems.

So, too, with the selection of compatible cards. Android Pay supports credit cards from MasterCard, American Express, Visa and Discover, but that's not the same thing as supporting all debit cards branded under one of the big four.

For example, I attempted to link a Chase (MasterCard) debit card to Android Pay, only to find out that Chase is one of the largest omissions from Google's pantheon of major U.S. banks that support the app.

But the number of stores that support Android Pay, which Google claims is now up to "over one million locations across the U.S." is key to the success or failure of this app. Not living in an area with a Walgreens or Rite Aid anywhere nearby (I apparently live in CVS country), and not wanting to buy a video game, pet food, office supplies or popular clothes for highschoolers, I ended up at the McDonald's for my live trial of Android Pay.

Not being sure how well -- or if -- Android Pay would work, I walked inside, rather than cause a horn-inducing delay in the drive through. After my order was punched in (a number four, if you're wondering), I asked if I could use Android Pay. Not knowing any specifics about it, the cashier just asked me to swipe the phone where iPhone people had done the same.

So I unlocked the Nexus 6 and placed it on the receiver.

It took about five seconds -- about twice as long as was comfortable, being the only person whipping out a smartphone to pay for a burger -- before the terminal activated an Android Pay logo on my screen, and that was it! I got a paper receipt at the counter, and almost as fast, an Android Pay push notification receipt as well.

Tap That App

I would recommend this app, but with the caveat that you'll be an early adopter and many won't find Android Pay as useful, or simply as useable, as promo ads portray. Not yet at least.

Google has tried before and failed to implement device payment with Google Wallet, and several third-party Android companies have been hacking away at the "tap and go" idea for years, without major success, but this time might be different.

I say without "major success," because real success in payments is something approaching the adoption of the credit card: Something anyone can use at nearly any place money is exchanged for goods and services (with the exception of most of my favorite bars in Brooklyn).

What's different now -- what may make this the moment for the "real" success of mobile payments -- is that both sides of the iPhone / Android divide are using the same basic technology that works almost identically, and more stores are adding mobile checkouts to their registers.

The race for "Pay" dominance has just started, but it's a race that no one can win if everyone isn't competing on the same track.