Events and conferences
Swap details at a stand, with or without wifi
A conference hall is the worst connectivity in the world and the best place to meet people. The offline code carries the contact details in the code itself, so a scan still saves the contact when the venue wifi has given up.
What that looks like
A code that works offline
The offline variant encodes the contact directly, so a phone scanning it needs no network at all to save it.
Scan the cards you are given
Photograph a paper card and the details are read off it, shown for correction, and saved — nothing is stored until you confirm.
Follow up while it is warm
Contacts you capture are yours, with a reminder when one has gone a few days without a follow-up.