If it is about Nostr apps, I was thinking the other day about something like zap-credit. You give a credit to another npub through lightning and you demand from the receiver certain amount of money back in certain moment in the future (maybe under certain conditions). If the zap-loan is not correctly payed back, evidence will remain in the hash of the event. That would give me a sort of ledger of history about who is diligent with his credit and who is irresponsible. That would help me fund nostr developers that I consider trustworthy but it's not exclusive to Nostr, it could be any entrepreneur in the world