Skuzee
My wireless router is reserving a certain IP address for my phone by MAC address.
It's also not broadcasting is SSID and is password protected with a WPA2-PSK key.
The Arduino Yun, using its Bridge library, can execute shell command PING and periodically check to see if my phone is on the network.
I retrofit my deadbolt with a hobby servo to be controlled via the Arduino when my phone is detected on the network or when an inside "Door Unlock" button is pressed.
A door sensor will hold the lock until the door has been opened and closed again. it also prevents the lock from locking the door open and can give me feed back on when the door is opened without the servo being actuated. (i.e. someone used the key)
Picked up a fancy box from the Lobby of a Brand Name Hobby Store. 
I connected the servo and a few wires to the Arduino Yun to simulate the door button and door sensor. I'm happy to report that I've now got a simple program to open the door AND a small program that can ping my phone. Running shell commands, and capturing results was surprisingly easy and straight forward. I could share code if anyone is interested. 
Here's the disassembled inner lock face.
I removed the facade of the dead bolt and milled a relief to accept the servo neatly. 
I had to ream the screw holes a little deeper to clear the bottom of the servo. I drilled and tapped the bolt holes.
I'm using a tiny piece of acrylic I slotted and screwed to a servo arm to twist the linkage.
amr.mostaafaa
Robotic Arm&Hand
Pete Hoffswell
Smalls
Wow cool. Can you send the attachment you used to attach the servo to the metal rod in the deadbolt