If you want to build an app which supports contactless payments than there are few things that you would have to consider.
Create your android mobile app which uses "Host Card Emulation". Using this feature you can use the NFC device on you phone to act as a card. This is one of the operation mode supported by android NFC.
OK, thanks. So two things I failed to figure out are: 1. I have a card (PAN, expire date, CVV2, track1, track2). How to add it to the phone HCE service? 2. I got th information from APDU (wich is the byte array). How to turn it to the data wich I have to send to VIsa Checkout (amount, currency, etc)?
GBWhatsApp - It will help you to get rid of most of those restrictions that the official version imposes on you. In simple words, the gbwa is a modded application which has some extra features that you won’t be able to find in the stock version. Some of the most noteworthy and popular features of the gbwa mod are hiding blue tick, online status, last seen, theme customizations and the brand new auto-reply.