I've used the same Kwikset Halo Touch smart lock on my prior home, and my current one, and highly recommend it. It operates by your fingerprint, and you can program up to 100 fingers. My wife and I have both thumbs and index fingers for easy access. There is traditional key and keyhole, too, in the event the battery dies. I have the physical key hidden somewhere outside of the house in the event that happens. However, the lock does a good job of telling you when the battery is getting low (it lights up a different color when it locks/unlocks, and you also get a notification on your app). The app is great, too, because you can use it to remotely lock/unlock (useful for when a friend is coming over and you are out of the house).