Shared or lost keys can unlock the door to trouble. When the "key" to your house is on your phone, though, or entered into a keypad, you don't need to worry as much about the possibility of untrustworthy people entering unnoticed. When you upgrade the deadbolt on your door with the August Smart Lock, you'll get greater control over who enters your home and when. Create temporary virtual keys for guests who are scheduled to arrive at prearranged times, or simply buzz them in at a moment's notice from your phone. For peace of mind, you can check back on the app for a full log of recent visitors. Available on Amazon; $199.