Nuki Smart Lock change your smatphone into a smart-key. You could install your Smart Lock on the cylinder and use your keys.
Installation is finished after 3 minutes without drills and screws.
If you use the Nuki App, you could assign virutal keys to your families and friends to everytime or a limited time.
Also, you could know when and who closed the door by the key and if the main door is closed correctly.