This sounds like an extended version of Leon Brocard's cpanstats. Although I believe that it's not working at the moment because Leon just moved to a new server and is still rebuilding stuff. cpanstats is only about producing summary data though, not about finding who is using what.

When I have my module author hat on, I would indeed find it useful to know what sorts of platforms my code is being used on, and who is using it on weird platforms like VMS and Windows that I can't test on. But I can also understand the concern of some people that they don't want to publicise which modules they use. I can even understand why some people might not want to let the author know. So I ask for feedback, and I try to give people an incentive to give me feedback. Bug reports and feature requests from people who I've heard from before get a higher priority.