Proposed benchmarking functionality to provide deeper insight into the performance of WordPress.

I've been trying to figure out how I could better gain insight into who WordPress is performing. After a great deal of thought, trial and error, here is a proposed API for benchmarking complete with integration in the hooks API.

The things that I remain unsure about include:
* Should we offer more parameters to the wp_benchmark function?
* Should we store benchmark groups in an option? Or should it be managed by an array in wp-config?
Is there a way to keep the wp_benchmark function generalized while having less code wrapping the benchmark target (such as in the hooks function).