It's still yet to become a thing outside of the US despite being a thing for quite a bit now. For those in the US the latest version of Android Pay fixes a rather annoying bug where the app would not show up loyalty or membership cards on a second device.
To send your thoughts on the app there is now a feedback option and if you want to check out what banks are working with the app tap see participating banks and you'll be directed to the Android Pay website.
Previous versions of the Android Pay app haven't been downloadable for quite a few people outside the US and although this one is it still doesn't work.
Get the update from APK Mirror via the link.