Our mission at Runscope is to bring a level of visibility to your app's API and backend service calls that has not been previously possible. Runscope URLs are a really easy way to capture traffic in any client. If you're making a lot of calls however, constructing the URLs each time can be a bit tedious. We've previously streamlined the process for developers who use Requests for Python with our requests-python module.
Guzzle is an up-and-coming PHP HTTP client written by Michael Dowling that powers many API client libraries, including the official AWS SDK for PHP. Thanks to it's powerful extensibility model, plugging in Runscope for debugging and inspecting calls was super simple.
To build the plugin we worked with Luis Cordova, a PHP developer from Peru and the author of Symfony2 Ecommerce: The Lean-Book. Luis also built a Runscope Symfony2 Bundle which he wrote more about on his blog.