This is pretty interesting. JSHint has had this feature for a while, but it's cool to have a tool like this completely stand alone. I could imagine putting together a custom static analyzer such as jshint using grunt and a bunch of these smaller modules.
Btw this was not meant to replace jslint/jshint etc.
It was meant to be a programming time niche-filler between 11:30pm and 3:30 am (to end off the day with something useful).
I am happy if the tool is useful for anyone, but making it a more general static analysis tool will probably require a lot of more work.