Most door locks can be automated by fitting a large servo - and of course then be controlled by your Arduino at whim, however as the concept of home automation is increasingly popular more users are looking for a remote-control locking solution.
One solution to this problem is to interface an Arduino/servo combination with the Twilio cloud communication system via a PC - which then allows for control via SMS text message. This has been demonstrated by the Jonathan Gottfried and works without much complication.
Furthermore this could be the framework for remotely-controlling almost anything connected to an Arduino via SMS - so visit the Twilio blog for complete code and notes. And for more, we're on facebook, Google+, and twitter - so follow us for news and product updates as well.
If you're looking for an Arduino Uno-compatible board for various projects, choose what tens of thousands of others have done and use our Freetronics Eleven - the Arduino-Uno compatible with low-profile USB socket, onboard prototyping space and easy to view LEDs: