Yale Approach is the smart retrofit option I recommend when you want to keep your current deadbolt and key. I installed it in about 20 minutes, and it adds app control, auto-locking, and activity history, plus multiple ways to unlock (Bluetooth, key, keypad).
Pros
+Retrofit design lets you keep your existing lock and key
+Quick install with a screwdriver (about 20 minutes for me)
+Door open/close sensing enables auto-locking after configuration
+Multiple unlock options (Bluetooth, key, keypad)
+Guest codes with custom active time windows
Cons
-Keyhole-side stability was tricky solo; included tape didn’t hold well for me
-Keypad adhesive didn’t stick perfectly on my door; may need mounting accessories
-Wi-Fi requires a separate bridge plugged into a nearby outlet