Fill a box with small things for one friend — a note, a doodle, a badge, some of your NovaCoins — then send them a single link. They unwrap it one thing at a time.
The whole box is inside the link itself — there is no server here holding it. That is why it works with no account, and also why a link that gets cut short by a chat app will not open. If it does not work, paste it as plain text rather than letting the app shorten it.
Everything you type is checked the same way names are. Boxes are for people you actually know. Nothing is uploaded — the link is the box.