Where were these when Henry was born?

I was walking around Buy Buy Baby the other day and saw this genius product. I wish I had known about them sooner so I could’ve saved myself thousands of dollars on a Doc Band and just got a couple of these for $20! They should send every new mom home from the hospital with one instead of a little knit cap (though the knit caps are pretty dang cute).

Has anyone used one? Do they work?