Car keys and house keys could be implemented as U2F tokens. A person could carry a single device, which could be a discrete token like a Yubikey, or virtualized

Car keys and house keys could be implemented as U2F tokens. A person could carry a single device, which could be a discrete token like a Yubikey, or virtualized in a phone, to authenticate to work, home, car, and computers. I wish Tesla would adopt U2F. They already have something that seems to be BLE/NFC for the Model 3.