This is a feature of iOS and macOS, at least. If you have a wifi network's password saved in your device, you can bring it physically close to another device th

This is a feature of iOS and macOS, at least. If you have a wifi network's password saved in your device, you can bring it physically close to another device that doesn't and it will ask whether you want to share. You have to affirm you want to give them the login before it will happen. Very handy when traveling as only one person in the group has to find and (mis)type the password :)