The first versions of most projects are self-contained applications. They work as-is, without any connection to other applications. It often isn't until a later release that there is focus on interoperability. [...] While this is an important steps toward application interoperability, there is often an important step missing. Most interoperable applications lack one final feature that allows full seamless integration: data sourcing, or the ability to get the data it needs from elsewhere.

He talks about two types of data sourcing - synchronization and federation (pulling the data as needed). He also gives a few examples of implementing this method in your application in things like your framework's models, abstracting out protocol connections and using web services (SOAP, REST) to make the connections. He also briefly touches on a very important topic to keep things in line - standards.

I figure the only way Google Voice could be improved is if it magically knew where I am and made my phones ring accordingly'"so that's exactly what I made it do. You can, too, with an Android phone, the Locale app, and a web server. The overall goal: have Google Voice know which phones to ring, based on your current location or situation.

You'll need a Google Voice account (obviously), some software for your phone and a remote web server running PHP 5 (with cURL and json functionality). You can then use the PHP script by passing parameters as to which phones to turn off and on and use the Locale tool to create the "situations" where it needs to make the switch.