On his site Fabien Potencier has posted about a feature added to Silex to help make debugging the flow of your application "more fun" - the Symfony web profiler.
One of the big advantages of both Symfony and Silex is that they are based on the Symfony HttpKernel component. [...] But handling HTTP requests with the Symfony HttpKernel also gives you a lot of free and optional features like a built-in reverse proxy written in PHP, easy handling of ESI and Hincludes (via the Fragment sub-framework), or the gorgeous Symfony web profiler.
The profiler provides information on which components were accessed, their memory consumption and how long they took to execute. The integration happens via the WebProfiler provider for Silex and is already integrated into the Silex skeleton base application.