It also based on Android and Arduino platform both of which are free open source software. In this paper, a system called door locks automation system using Bluetooth-based Android Smartphone is ...

The hack is still pretty hardware intensive, but Arduino fans will love this clever hack—especially if you're the type that locks yourself out of your room a lot.

Once communications are established a 32-bit sitecode can be read from any of the locks and immediately used to open the door.