You can always use your smartphone to unlock doors, but as a second credential you can also use Tags. A Tag is a physical device (contactless key fob) that works based on RFID. With a built in secured chip, an opening can be triggered by directly presenting the Tag to the lock.
A Tag replaces that ring of keys, and grants designated access to employees, guests or even cleaning services whenever it’s appropriate for them to enter. Simply assign a Tag to a user, and define when and where that Tag can go.