A couple suggestions

[jacobg]

Good job. I'm about to integrate it into my project.

A few suggestions (which I plan to do on my own):

1. rather than shutdown after maxInactive interval, instead store idle state
2. fire idle and wake events when state changes
3. advanced idle state management, where each listener can specify its own maxInactive interval

[arthurakay]

I like it. Feel free to PR if you are so inclined ;-)