I've done this project before, except I used Tropo + Arduino Ethernet + Twitter's API. Coding the server in Node.js is way easier, but requires a computer to remain on and connected to the Arduino in order to work.

Also, the duct tape will come off after around 100 locks/unlocks, so I eventually had to remake the whole thing with a 3D printed frame and shaft that would be secured to the door. My initial version was horrible, held together by glue/duct tape/cardboard/prayers.

If you want to turn the lock without the motor, you need to have the Arduino detach the servo after the rotation is complete. If you don't detach the servo, you'll damage the motor if you turn it by hand, because the internal tachometer will fight as hard as it can to maintain the servo's position.

Overall a very cool project and a great primer into using Node with Arduino.