I think one killer use case for nostr right now is online tuition.

Killer feature… a bookable calendar.

Tutor puts up some time slots in a public calendar and you can book a slot with a LN payment. The calendar then DM’s a webRTC link to both parties.

Tutors rise and fall by their reputation.

Thinking about this a bit more… you could do lots of things from math tuition to cocktail classes. Maybe even sell services and meeting time this way. Eg speak to a lawyer.

Relatively easy to build this on nostr.