GitHub: contact watchers
You want to contact all the watchers of a project. For instance, you want to notify them about some radical changes.
Simply click on the “Eye” icon that shows the number of watchers. It will list your followers.
Or, you can get the list of watchers through an API:
curl http://github.com/api/v2/json/repos/show/USERNAME/REPONAME/watchers?full=1 | python -mjson.tool