Sticker on the front door replaces a smart doorbell. Couriers tap 'I'm here' (webhook → push). Guests enter a PIN to see the guest Wi-Fi or instructions for the key safe.
One QR, two audiences. Couriers see a public 'I'm at your door' button that fires a webhook to the owner's phone. Friends with the PIN unlock a private page with the guest Wi-Fi, parking note, or key-safe combination.
Free tier includes 1 permanent QR and the recovery key — upgrade the slot with the exact modules this case uses whenever you need them.