One of the biggest home security mistakes people (a lot of people!) make is to have a "hide-a-key" located near their door. Putting a key to your house--where your family lives and most of your worldly possessions reside--three feet from your door just isn't wise. If you think professional burglars don't know to look under the door mat, above the door frame, or under that little rock next to the path, you're wrong.
The most obvious fix for this home security problem is not to have a spare key laying around. If you're truly concerned that someone in the family is going to lose the key and not be able to get into the house, it makes sense to install something like this number pad door lock.
Installing this attractive Schlage Camelot Deadbolt Keypad (or any number pad door lock) means nobody needs to worry about carrying a house key around any more. Just program in a code, and your door will open up the same way an ATM works.
This keyless entry system is easily reprogrammed if you decide you don't want the cleaning lady, eldest son who won't move out, etc. not to know the combination any more (a lot simpler than having locks rekeyed!), and it's only supposed to take 30 minutes to install, so it ought to be a simple weekend project.
Other perks with the Schlage lock (which is available in a number of finishes, so you can get one that matches your door) include illumination for the keypad (so you can see what you're doing at night), a free-spinning keyway to prevent wrench attacks, and a key override system in case you forget the programming code down the line.
This particular number pad door lock costs about $275, though it's on special for quite a bit less at Amazon as I write this: