I have the remote deadbolt on my back door which works with a key fob. It is battery operated and looks slightly bigger than a normal lock. It also has a keypad where I could mount it anywhere near the door to operate the lock. They are usually mounted on the inside of the door frame outside the door of course. I haoppen not to be using mine though. The system works OK. I have seen it at another house working with the keypad. I don't remember the manufacturer.
I also have a remote entry front door, but that is controlled by a phone system from inside the house. It's like a "Buzz you in" type of door. You don't hear the "buzz" though. It's just a 'click' and the front door opens after you talked with the person at the door. It's great when you're in a far room of the house, basement, office etc... and someone rings the front door. Talk to them and 'click' them in. The phone system is a Panasonic system and the door opener looks like this...
http://www.smarthome.com/5190s12.html smarthome has a lot of these types of locks. Check them out for some ideas.