Does this really beat a printed BUSY clipart taped to my screen? It's far from the first product I see like this and the question is always the same.
It does cover people interrupting you to ask “ok but how long will you be busy?” :) unless you want to replace your taped clip art every minute or so.
At this price, you can get a second Monitor facing outward and display how long you’ll be busy on that. In fact, you can get 2 monitors and another computer and have some change left. This is a cool product, especially design-wise, but there are much cheaper solution for this very small problem.