I've actually been thinking about that. I was thinking of a more general personal metrics site, though. Weight, personal finances, freethrow percentage, whatever you want to track, give people the tools they need to track whatever needs tracked in their lives.
Figure it's worth jotting down in the "any other ideas" section of the app, anyway.
Someone's also helpfully put the tools that the book describes online at http://infohost.nmt.edu/~carmiac/whdt/whdt.cgi