Some models use your existing keyed cylinder and deadbolt hardware and attach to the inside of your door, while others require that you remove your existing interior and exterior escutcheons and replace the deadbolt and strike hardware. Smart locks can be opened and closed using a mobile app and will send a notification when someone locks or unlocks a door, and most allow you to create permanent and temporary access schedules for family members and friends based on specific hours of the day and days of the week. Features to look for include geofencing, which uses your phone's location services to lock and unlock the door, voice activation using Siri HomeKit, Google Assistant, or Amazon Alexa voice commands, support for IFTTT, and integration with other smart home devices such as video doorbells, outdoor cameras, thermostats, smoke alarms, and connected lighting. Best Smart Home Security Systems Featured in This Roundup:ADT Pulse ReviewMSRP: $28. 99 at Pros: Fast and knowledgeable service reps. Many components available. Support for third party devices. Solid mobile and web apps. Cons: Expensive. Requires three year contract with hefty termination penalty. Some Pulse peripherals require third party mobile apps.