Something like ten years ago Facebook messenger would by default add the user’s location to every message visible to the recipient. And even worse, unless you disabled this feature, it would give away the distance from you to all your contacts, even ones you had never even had a conversation with. In real time, so someone could easily use it to triangulate you. Meta is a very creepy company.
they even exposed it via an api, i remember building poc “friend maps” that showed where everyone was without their consent.
Oh dear, am I the only one who remembers the marauders map? I saw a bunch like you were talking about, but the Harry Potter version was exceptional.