Looks like it's only available for smartphones and tablets, not for computers. Probably because on smartphones and tables they have their own app and don't have to rely on a browser.
If they do, they should be able to get this to the web version of Netflix.
(Laptop screens are great for watching video content on e.g. a flight or train ride. Bringing an extra piece of hardware like a tablet just for this purpose seems silly. Phone screens offer poor ergonomy. They are only really a decent compromise on a bus or a subway, or similar.)