Not only that, but if you’re returning this status code you’re almost certainly doing something wrong or user hostile.
I think the appropriate action would be a client sends an HTTP HEAD to the service, which responds 200 "TEAPOT".
http://fellowproducts.com/shop/staggekg/
I have the plain EKG, and quite like it.
However, both are designed for pour-over coffee, so can’t correctly return 418.