This app was mentioned in 7 comments, with an average of 1.86 upvotes
If you apply for a Barclaycard Visa, or their Hilton Honors alternative, their myBarclaycard app allows contactless payment using the app. I've tested it at M&S and it worked fine, and other users have tested it on the tube and TFL.
Up to £30 without a PIN, £30 to £100 requires PIN entry.
First Direct and HSBC are signed up to work with ZAPP.co.uk for app payment, but it's way behind schedule.
Barclaycard already have an app - but it's a bit annoying and I may stop using it in favour of Android Pay.
Shame TSB aren't on board (as they are with Apple Pay) - the 5% cashback on contactless transactions is nice.
also: link in case you wanna edit this into your OP:
https://play.google.com/store/apps/details?id=com.barclays.bca
Can you barclaycardapp
If you get a Barclay's Visa, their app allows NFC payment