The whole idea is a privacy minefield, so it would have to be very carefully designed and implemented, of course making it opt-in. But still, should we even pursue this idea?
So that, for example, even if I met someone just briefly, they can still later see the contact information that I am willing to provide.
Wouldn’t that make it much easier to connect with people who live close to you?
Are there any relevant projects or ideas that already exist?
Nintendo had a feature like this implemented in the 3DS called StreetPass. When you passed someone else with a 3DS it would share some information (like game data) that you could later review.