Wow, a tool like that is long overdue. By benchmarking your dev environment with production you could also "trend" how your development releases should do in the production environment. I'm sure that most development shops dev environments are nothing like the production hardware.

Question though, from SQL viewpoint how would this be different than capturing a trace and then playing it back? Then the next question would be how to systematically increase (scale up) the work load of the captured trace (with realistic database load). That is probably the hard part of the solution.