I was about to start working on an identical tool as my side-project.

Couple of thoughts:

* Devise a "pagerank for packages" algorithm - number of Github stars, how actively they're maintained, number of issues/contributors/etc.

* For monetization offer a service similar to https://www.versioneye.com (found out about them on HN as well, after I had the idea). You're going to crawl the packages either way.

Best of luck!