We've created and made available new package
https://www.npmjs.com/package/stellar-sign
It allows to send @PapayaBot users payment requests. It can be used in any ecommerce environment, payment widgets, etc.
It's entirely on stellar blockchain, no additional API needed, no links, QR codes, etc. The only thing required from user is his federated name where to direct the request.
Whenever you want PapayaBot user to pay you - you initiate transaction and user receives this prompt
It can be extended to support multi-signature and implemented by other wallets, if they wish to.
Here couple of usage examples: