Here’s some setup instructions from nostr:npub1lqs30x7466guvx6r2cek8z9d4hpucycy7j08wx58cwx70m206q3qrscejr

I think under the hood, a 3rd party app just monitors nostr events for reactions of a specific type. For example when you tap 🤙 on Damus, Zapplepay will notice that you did that and send sats to the owner of the note you reacted to on your behalf.

nostr:note1axfmanfsm78y6nkhd4p4r29nprem2yxx5frrvwqtrah49336mmaqt5ks6v