Thanks to the ease of adding Internet-based connectivity to a Raspberry Pi, it lends itself to all sorts of remote-control and data gathering applications. One example of this is by Arvind Ravulavaru who has documented controlling a Raspberry Pi not only as a local doorbell, but one that can be controlled over the net via node.js and python.
The resulting project simply controls a GPIO pin from a remote, web-enabled device - however thanks to the clarity of Arvind's work you can use this as a framework for all sorts of applications. A quick demonstration of the remote doorbell is shown in the following video:
If you need to connect external circuitry to your Raspberry Pi such as the project above, consider our PiBreak board. It provides labelled breakout pins for all GPIOs, a large prototyping area with solder pads, and power rails for easy power connection:
Furthermore the PiBreak also includes mounting hardware to firmly attach it to your Raspberry Pi using a nut, bolt, and spacer - and is compatible with all revisions of both model A and B Raspberry Pi computers. For more information about our PiBreak board, our Getting Started guide, and to order - visit the product page.