I loved these when I was a kid growing up in NZ. At work I would pull the cord, and when the water boiled it would whistle and turn itself off. I'd then come back to the kitchen and make a pot of tea. The whistle would have alerted my coworkers to the fact that it was teatime (even when it really wasn't) and they would come into the tearoom for their morning or afternoon break. This way I could manipulate my coworkers to take a break whenever I pleased!
I haven't seen one in California. Must be an Australasian thing. It's especially useful where there is no provision for hot water.