We used one here in the UK when our daughter was young and had a series of chest infections (coughing throughout the night etc.) at the recommendation of the do

We used one here in the UK when our daughter was young and had a series of chest infections (coughing throughout the night etc.) at the recommendation of the doctor (and it seemed to work). It might not be big, but there is a market for most things, most places. Your (and my) experience is often not generalisable completely.