Primal does it with a custodial wallet provided by nostr:npub1ex7mdykw786qxvmtuls208uyxmn0hse95rfwsarvfde5yg6wy7jq6qvyt9 and direct sats purchases for those wallets from ApplePay. It’s a nice experience but even though it’s open source it isn’t something you could easily run on your own.